Information terminal device with power control means

0001The present invention relates to an information terminal device according to the preamble of claim 1 and an input/output control method according to the preamble of claim 6.

0002In general, a portable terminal device is driven by a battery. If a remaining quantity of the battery is reduced, input/output operation such as communication is not carried out stably, and there is an unfavorable possibility that an error may be generated in data which is input or output. For such a case, technique for stopping the communication function of the portable terminal device when the remaining quantity of the battery is small for avoiding a failure due to shortage of the battery remaining quantity is disclosed in Japanese Patent Application Laid-open No.<patcit id="pcit0001" dnum="JP6067766A"><text>6-67766</text></patcit>.

0003<figref idref="f0001">Fig.1</figref> is a functional block diagram showing a functional structure of the above mentioned conventional portable terminal device.

0004In this portable terminal device, a judging means 65 compares a remaining quantity of a battery 61 detected by a battery remaining quantity detecting means 63 and a battery volume necessary for communication for a communicating means 62 estimated by an estimating means 64, thereby judging whether there is enough battery remaining quantify necessary for communication. As a result, if there is enough battery remaining quantity necessary for communication, the judging means 65 permits the communicating means 62 to communicate, and if there is not enough battery remaining quantity/power necessary for communication, the judging means 65 prohibits the communicating means 62 from communicating. If the communication is inhibited, the judging means 65 suppresses other function by function suppressing means 67, and newly judges a battery remaining quantity necessary for communication from electricity consumption of suppressed function, thereby avoiding a failure of communication due to shortage of electricity.

0005Moreover, some communicating means such as modems can change communication speed, and electricity consumption may be varied depending upon change in the communication speed. However, in the above mentioned conventional example, a variation in electricity consumption is not taken into account. Therefore, when the communication speed is changed in the above mentioned conventional example, a program of the estimating means 64, i.e., an operating system of the portable terminal device must be changed.

0006Further, among portable terminal devices, some communicating means are exchangeable such as PCMCIA modems each having different electricity consumption. However, a case in which the modem is exchanged is not taken into account in the above mentioned conventional example. Therefore, in the conventional example, a program of the estimating means 64, i.e., an operating system of the portable terminal device must be changed if the communicating means is exchanged.

0007Furthermore, in the above mentioned portable terminal device, only a case in which operation of a single communicating means is controlled is taken into account. However, there is a case in which one portable terminal device includes a plurality of communicating means such as a LAN card and an infrared modem in addition to a modem. Such a case in which other communicating means are added is not taken into account in the above mentioned conventional example. It is possible, whenever a communicating means is newly added, to add another estimating means 64 which corresponds to the added communicating means, but in such a case also, the operating system must be changed.

0008Also, when the operation becomes unstable due to decrease in electricity, and there is a problem in quality of data, such a problem arises also in other input/output means in addition to the communicating means. However, an input/output means other than the communicating means is not taken into account in the conventional example.

0009<patcit id="pcit0002" dnum="US5532935A"><text>US 5 532 935</text></patcit> discloses an information terminal device according to the preamble of claim 1. <patcit id="pcit0003" dnum="US5511205A"><text>US 5 511 205</text></patcit> discloses a related information terminal device.

0010It is an object of the present invention to provide an information terminal device and an input/output control method capable of preventing the operation of an input/output device from being unstabilized due to shortage of battery volume without changing an operating system even when electricity consumption of the input/output device is varied due to setting or the input/output device is exchanged or newly added.

0011An information terminal device driven by a battery according to the present invention comprises the features of claim 1.

0012In the information terminal device, when the judging means judges that there is enough battery remaining quantity, input or output of data by the input/output device is permitted by the permitting means. Therefore, when the battery remaining quantity is not enough, data is not input or output in an unstable operational state. Further, in the information terminal device, the electricity consumption of the input/output device stored in the driving means is registered in the electricity consumption registering means. Then, the judging means judges in accordance with the registered electricity consumption. Therefore, even when the input/output device is exchanged or newly added, it is unnecessary to make changes in any other portion than a driving means corresponding to such exchanged or newly added input/output device.

0013In the above information terminal device, electricity consumption of the input/output device may be varied depending upon a setting of the driving means.

0014In this case, electricity consumption corresponding to the changed setting is re-registered in the re-registering means by changing the setting of the driving means by the setting changing means, and the input/output device can be operated in accordance with the re-registered electricity consumption. Therefore, it is possible to allow the input/output device to operate needed operation as much as possible. In this case also, it is unnecessary to make any change in other portions.

0015In the information terminal device according to claim 3, the electricity consumption of the input/output device measured by the electricity consumption measuring means is registered in the electricity consumption registering means. Therefore, when the input/output device is used a second time or subsequent time, the judging means judges in accordance with this registered electricity consumption. For this reason, even if the electricity consumption of the input/output device corresponding to the driving means is not stored, the same effect as that of the information terminal device of the first aspect can be obtained. Further, even if the input/output device is changed or newly added, it is unnecessary to make change in other portions other than the driving means corresponding to the changed or newly added input/output device.

0016According to the present invention, when the battery remaining quantity is not enough, data is not input or output in unstable operational state. Further, when an input/output device is changed or newly added, it is unnecessary to make a change in any portion other than the driving means (driver) corresponding to such a changed or newly added electricity consumption device.

0017Further, when electricity consumption of the input/output device is varied by the setting of the driving means (driver), it is possible to allow the input/output to operate as much as possible by changing the setting of the driving means (driver) to a lower electricity consumption side.

BRIEF DESCRIPTION OF THE DRAWINGS

0018<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig.1</figref> is a functional block diagram showing a functional structure of a conventional portable information terminal device;</li><li><figref idref="f0002">Fig.2</figref> is a block diagram showing a circuit structure of a portable information terminal device according to an embodiment of the present invention;</li><li><figref idref="f0003">Fig.3</figref> is a functional block diagram showing a functional structure of the portable information terminal device according to the embodiment of the present invention;</li><li><figref idref="f0004">Figs.4A and 4B</figref> are views for showing an address structure of a driver shown in <figref idref="f0002">Fig.2</figref>, wherein <figref idref="f0004">Fig.4A</figref> shows a case in which a corresponding hardware has a single electricity consumption value, and <figref idref="f0004">Fig.4B</figref> shows a case in which the electricity consumption value of the corresponding input/output hardware can be changed by setting;</li><li><figref idref="f0005">Fig. 5</figref> is a flow chart showing a procedure for executing input/output function in the portable information terminal device according to the embodiment of the present invention;</li><li><figref idref="f0006">Fig.6</figref> is a flow chart showing a procedure for checking a battery remaining quantity in the portable information terminal device according to the embodiment of the present invention;</li><li><figref idref="f0007">Fig.7</figref> is a flow chart showing a procedure of a subroutine for initializing the driver;</li><li><figref idref="f0008">Fig.8</figref> is a flow chart showing a procedure in subroutine for changing the setting of the driver; and</li><li><figref idref="f0009">Fig.9</figref> is a block diagram showing a circuit structure of a portable information terminal device according to a modification of the embodiment of the invention.</li></ul>

DESCRIPTION OF THE PREFERRED EMBODIMENT

0019A preferred embodiment of the present invention will now be explained with reference to the accompanying drawings

0020<figref idref="f0002">Fig.2</figref> is a block diagram showing a circuit structure of a portable information terminal device according to the embodiment of the present invention.

0021As shown in <figref idref="f0002">Fig.2</figref>, the portable terminal device comprises a CPU 11, a ROM 12, a RAM 13, a battery 14, input/output hardware 15a to 15c, switches 16a to 16c and a battery remaining quantity measuring instrument (DET) 17. The CPU 11, the ROM 12, the RAM 13, the input/output hardware 15a to 15c, the switches 16a to 16c and the battery remaining quantity measuring instrument (DET) 17 are connected with each other through a bus 10.

0022The CPU 11 executes process programs which are stored in the ROM 12 and shown in the flow chart as will be described later. When the CPU 11 executes these programs, functions which will be described later are realized in the portable terminal device. The CPU 11 is provided therein with a timer 11a, and battery remaining quantity checking process which will be described later is carried cut in accordance with interrupt requested at predetermined time intervals from the timer 11a.

0023The ROM 12 stores data used by or in the process program of the CPU 11. The ROM 12 stores programs of an operating system which will be described later (here, this means an operating system in a wide sense, and this includes drivers) or application programs. The ROM 12 is a nonvolatile memory and thus, data is held even if the portable terminal device is turned OFF.

0024The RAM 13 is a volatile memory constituted by a semiconductor memory, and is used as a working area of the CPU 11.

0025In this portable terminal device, different addresses are allocated to the ROM 12 and RAM 13. The CPU 11 may directly read the process program from the ROM 12 and execute, or may transfer the process program stored in the ROM 12 to the RAM 13, and read the process program from the RAM 13 and execute. A program in which a setting of a driver is changed as will be described later is always transferred from the ROM 12 to RAM 13 and executed.

0026The battery 14 supplies electricity to various portions of the portable terminal such as input/output hardware 15a to 15c. The battery 14 may be a flashlight battery, a battery pack type battery, or a storage battery. The battery 14 may be one which is an external battery to be mounted to the outside the portable terminal device.

0027Although only three input/output hardware components 15a to 15c are shown in <figref idref="f0002">Fig. 2</figref>, the number of input/output hardware is not limited. Examples of the input/output hardware 15a to 15c are a keyboard for inputting characters or numbers, a liquid crystal display apparatus, a touch panel provided in front of the liquid crystal display apparatus, a disk device for reading and writing data on a floppy disk, a LAN card for sending and receiving, through LAN, data to or from another computer connected to the LAN, and a modem for sending and receiving data to or from another computer through telephone line. As will be described later, electricity consumption of some of the input/output hardware 15a to 15c may be varied by the setting.

0028The switches 16a to 16c are provided such as to correspond to the input/output hardware 15a to 15c, supplies or cuts the supply of electricity from the battery 14. The switches 16a to 16c may be hardware switches such as FET, or may be software switches for stopping driving function which will be described later for driving the corresponding input/output hardware 15a to 15c.

0029The battery remaining quantity measuring instrument 17 measures a remaining quantity of the battery 14.

0030<figref idref="f0003">Fig.3</figref> is a functional block diagram showing the function of this portable terminal device which is realized if the CPU 11 executes the process program stored in the ROM 12.

0031As shown in <figref idref="f0003">Fig.3</figref>, the function of this portable terminal device comprises an operating system 20, drivers 21a to 21c, application programs 22a to 22c, input/output hardware 15a to 15c, the battery remaining quantity measuring instrument 17, a function table 31, link information 32 and a working area 30 in which a electricity consumption value table 33 is written.

0032The operating system 20 executes input/output function which will be described later based on request from application programs 22a to 22c, and executes process of battery remaining quantity checking which will be described later based on interruption from the timer 11a provided in the CPU 11. When these processes are executed, the operating system 20 reads and writes the link information 32 or the electricity consumption value table 33. The operating system 20 writes the electricity consumption value on the electricity consumption value table 33 by a setting value indicated by the application programs 22a to 22c or a default value held by the operating system 20 when the input/output function is executed.

0033The drivers (device drivers) 21a to 21c respectively control the input/output hardware 15a to 15c to input or output. The address structure of the drivers 21a to 21c differs depending upon whether or not the electricity consumption of the corresponding input/output hardware 15a to 15c is varied by a setting value indicated by the operating system 20.

0034When the electricity consumption of the corresponding input/output hardware 15a to 15c is not varied by the setting value, each of the drivers 21a to 21c comprises driver header information 41, a driver body 42, input/output value header information 43 and electricity consumption value data 44 as shown in <figref idref="f0004">Fig. 4A</figref>.

0035When the electricity consumption of the corresponding input/output hardware 15a to 15c is varied by the setting value, each of the drivers 21a to 21c comprises driver header information 41, a driver body 42, input/output value header information 43 and a plurality of electricity consumption value data 44a to 44n as shown in <figref idref="f0004">Fig.4B</figref>.

0036The driver header information 41 includes information concerning a starting address of the driver body 42 and attribute of the driver. The driver body 42 is a program for controlling the corresponding input/output hardware 15a to 15c. The electricity consumption value header information 43 includes information concerning whether the number of the electricity consumption value of the corresponding input/output hardware 15a to 15c is one or more, and if the number of the electricity consumption value is more than one, the electricity consumption value header information 43 further includes information concerning associative relation between the setting value and the electricity consumption value data. The electricity consumption data 44, 44a to 44n are information concerning the electricity consumption of the corresponding input/output hardware, and the electricity consumption data 44a to 44n in <figref idref="f0004">Fig.4B</figref> are information corresponding to the respective setting values.

0037Referring back to the functional block diagram in <figref idref="f0003">Fig.3</figref>, the application programs 22a to 22c are programs for realizing functions such as word processor, spreadsheet program, database, schedule management or communication, and are executed under control of the operating system 20.

0038As described, the working area 30 is provided in the RAM 12.

0039In the functional table 31 which is written in the work area 30, input/output functions of the operating system 20 are listed and stored.

0040Electricity consumption values respectively corresponding to the input/output hardware 15a to 15c are written in the electricity consumption value table 33. When the electricity consumption of the input/output hardware 15a to 15c are not varied, the electricity consumption value data 44 of the corresponding drivers 21a to 21c are written in the electricity consumption value table 33. When the electricity consumption of the input/output hardware 15a to15c are varied by the setting value, among the electricity consumption value data of the corresponding drivers 21a to 21c, only electricity consumption value data corresponding to the setting value is written.

0041The link information 32 indicates which of the input/output hardware 15a to 15c should be used to realize the input/output function of the operating system 20 written in the functional table 31. The order of priority is set in the link information 32, when the link information 32 is released as will be described later, such information is released from the increasing order of the priority.

0042The operation of the portable information terminal device will be explained below.

0043First, when this portable information terminal device is turned on, a boot program is operated and the operating system 20 is started. The operating system 20 registers input/output function realized by the operating system 20 in the functional table 31, reads the electricity consumption value data 44, 44a to 44n based on default setting value, and registers the same in the electricity consumption value table 33. Then, the link information 32 is set with respect to the various function registered in the functional table 31 and electricity consumption values of the hardware 15a to 15c registered in the electricity consumption value table 33.

0044Then, any of the application programs 22a to 22c are executed by a user's request from the portable terminal device.

0045Next, it is supposed that input/output is requested by the application program 22a to 22c executed by the user's request. At that time, the application program transfers a setting value of the drivers 11a to 11c executed by function of the operating system 20 that corresponds to a request stored in the functional table 31, and data to be input or output, to the operating system 20 as parameters. Then, based on the transferred parameters, the processing "execution of input/output control" which is a function of the operating system 20 and is shown in the flow chart in <figref idref="f0005">Fig.5</figref> is carried out.

0046When the processing of the flow chart shown in <figref idref="f0005">Fig.5</figref> is started, the CPU 11 first moves to a subroutine "initialize drivers" which will be described later, and initializes the drivers 21a to 21c corresponding to the function (step S11). By this "initialize drivers", the electricity consumption corresponding to the setting value of the driver is registered in the electricity consumption value table 33.

0047When the processing of the subroutine of "initialize drivers" is completed, the CPU 11 returns to a main routine, and obtains the link information 32 from function registered in the functional table 31 that is requested by the application programs 21a to 21c (step S12). Then the CPU 11 judges whether or not the link information 32 is set with respect to the function (step S13).

0048If it is judged that the link information 32 is not set with respect to the function in step S13, the processing is advanced to an error processing in step S24 which will be described later.

0049If it is judged that the link information 32 is set with respect to the function in step S13, the CPU 11 obtains an address of the electricity consumption value in the electricity consumption value table 33 from the set link information 32 (step S14), and reads the electricity consumption value based on the obtained address (step S15).

0050Next, the CPU 11 obtains a remaining quantity of the battery 14 measured by the battery remaining quantity measuring instrument 17(step S16), and estimates a continuous operational time during which the corresponding input/output hardware 15a to 15c can continuously and stably be operated with the obtained remaining quantity of the battery 14 (step S17). Further, the CPU 11 calculates a function completing time that is necessary for completing the input/output function from the setting value of the driver transferred as the parameter and an amount of data to be input or output (step S18). The CPU 11 compares the continuously operational time estimated in step S17 and the function completing time calculated in step S18, and judges whether or not the continuous operational time is equal to or longer than the function completing time (step S19).

0051If it is judged that the continuous operational time is equal to or longer than the function completing time in step S19, the processing is advanced to step S20 which will be described later.

0052If it is judged that the continuous operational time is shorter than the function completing time in step S19, the CPU 11 judges whether it is possible to change the settings of the drivers for operating the input/output hardware 15a to 15c by the functions (step S21).

0053If it is judged that it is not possible to change the settings of the drivers in step S21, the processing is advanced to an error processing in step S24 which will be described later.

0054If it is judged that it is possible to change the settings of the drivers in step S21, the CPU 11 judges whether or not there is any other setting value capable of further reducing the electricity consumption of the corresponding input/output hardware 15a to 15c (step S22).

0055If it is judged that there is no setting value capable of further reducing the electricity consumption in step S22, the processing is advanced to error processing in step S24 which will be described later.

0056If it is judged that there is another setting value capable of further reducing the electricity consumption in step S22, the CPU 11 moves to a subroutine of "change of setting of driver" which will be described latter, and the setting of the drivers 21a to 21c corresponding to this function is changed (step S23). The electricity consumption value whose electricity consumption is lower by one level is registered in the electricity consumption value table 33.

0057When the processing of the subroutine of "change of setting of driver" is completed, the CPU 11 returns to the main routine, and returns back to step S14, the same processing is continued based on the electricity consumption value newly registered in the electricity consumption value table 33.

0058Step S20 corresponds to a case in which there is enough remaining quantity of battery 14 for executing the function stably. Therefore, the CPU 11 executes the program of the driver body 42, and operates the corresponding input/output hardware 15a to 15c. With this operation, the corresponding input/output hardware 15a to 15c input or output data requested by the application programs 22a to 22c. Then, the processing of this flow chart is completed.

0059Step S24 corresponds to a case in which there is not enough remaining quantity of battery 14 for executing the function stably. Therefore, the CPU 11 returns information rejecting the input/output of data requested by the application programs 21a to 21c as parameters to the application programs, and conducts error processing for informing the user of error by displaying to that effect or alarming. Thus, the processing in the flow chart is completed.

0060Further, in the portable terminal device, an interruption is generated at predetermined time intervals from the timer 11a, and in accordance with the interruption, "check of battery remaining quantity" which is a function of the operating system 20 and which is shown in a flow chart in <figref idref="f0006">Fig.6</figref> is conducted.

0061When the processing of the flow chart in <figref idref="f0006">Fig.6</figref> is started, the CPU 11 obtains a remaining quantity of the battery 14 measured by the battery remaining quantity measuring instrument 17 (step S31). Next, the CPU 11 sequentially obtains electricity consumption values in the electricity consumption value table 33 linked by the link information 32 from the functional table 31, and estimates the continuous operational time during which the corresponding input/output hardware 15a to 15c can continuously and stably operate with the remaining quantity of the battery 14 obtained in step S11 (step S32). The CPU 11 judges whether or not all the continuous operational times estimated in step S32 are equal to or longer than a predetermined value (step S33). These predetermined values of the corresponding input/output hardware 15a to 15c may be different.

0062When all the continuous operational times are not equal to or longer than a predetermined value in step S33, i.e., when any one of the estimated continuous operational times is not equal to or longer than the predetermined value, the CPU 11 judges whether or not the link information 32 is set between the functional table 31 and the electricity consumption value table 33 (step S34).

0063When it is judged that the link information 32 is set in step S34, the CPU 11 judges whether it is possible to change the setting value of a driver for operating any of the input/output hardware 15a to 15c (step S35).

0064When it is judged that it is not possible to change the setting value of the driver in step S35, the processing is advanced to step S38 which will be described later.

0065When it is judged that it is possible to change the setting value of the driver in step S35, the CPU 11 judges whether or not there is any other setting value capable of further reducing the electricity consumption of the corresponding input/output hardware 15a to 15c (step S36).

0066If it is judged that there is no setting value capable of further reducing the electricity consumption in step S36, the processing is advanced to processing in step S38.

0067If it is judged that there is another setting value capable of further reducing the electricity consumption in step S36, the CPU 11 moves to a subroutine of "change of setting of driver" which will be described later, and the setting of the drivers 21a to 21c corresponding to this function is changed (step S37). The electricity consumption value whose electricity consumption is lower by one level is registered in the electricity consumption value table 33.

0068When the processing of the subroutine of "change of setting of driver" is completed, the CPU 11 returns to the main routine, and returns back to step S32, the same processing is continued based on the electricity consumption value newly registered in the electricity consumption value table 33.

0069In step S38, the CPU 11 releases the link information 32 having the lowermost priority among the set link information 32. The CPU 11 returns to the processing of step S32, and the same processing is continued in accordance with the setting of the new link information.

0070When it is judged that the link information is not set in step S34, the shortage of remaining quantity of the battery 14 is displayed and alarm is given for warning the user of the shortage of remaining quantity of the battery 14 (step S39). Then the processing of the flow chart is completed.

0071On the other hand, when all the continuous operational times are equal to or longer than the predetermined value in step S33, the flow chart is completed as it is.

0072Processing of subroutine of "Initialize of driver" in step S12 will be explained with reference to the flow chart in <figref idref="f0007">Fig.7</figref>.

0073When the processing is started, the CPU 11 reads the electricity consumption value header information 43 of the corresponding drivers 21a to 21c (step S41). The CPU 11 judges whether or not the electricity consumption value is varied by the setting value from the read electricity consumption value header information 41(step S42).

0074When it is judged that the electricity consumption value is not varied by the setting value in step S42, the CPU 11 reads the electricity consumption value data 44 (step S43). Then, the processing is advanced to step S45.

0075When it is judged that the electricity consumption value is varied by the setting value in step S42, the CPU 11 refers the electricity consumption value header information 43 and reads the electricity consumption value data corresponding to the setting value among the electricity consumption value data 44a to 44n (step S44). Then, the processing is advanced to step S45.

0076In step S45, the CPU 11 registers the electricity consumption value data which is read in step S43 or S45 in corresponding address of the electricity consumption value table 33. The CPU 11 further carries out other initializing process such as initialization of the driver body 42 (step S46), and returns to the main routine.

0077Processing of subroutine of "Change in the setting of driver " in steps S23 and S38 will be explained with reference to a flow chart in <figref idref="f0008">Fig.8</figref>.

0078When the processing is started, the CPU 11 reads the electricity consumption value header information 43 of the corresponding drivers 21a to 21c (step S51). The CPU 11 judges whether or not the electricity consumption value is varied by the setting value from the read electricity consumption value header information 41 (step S52).

0079When it is judged that the electricity consumption value is not varied by the setting value in step S52, the processing is advanced to step S55.

0080When it is judged that the electricity consumption value is varied by the setting value in step S52, the CPU 11 refers the electricity consumption value header information 43 and reads the electricity consumption value data corresponding to the setting value among the electricity consumption value data 44a to 44n (step S54). Further, the CPU 11 registers the electricity consumption value data which is read in step S53 in the corresponding address of the electricity consumption value table 33 (step S54). Then, the processing is advanced to step S55.

0081In step S55, the CPU 11 conducts the processing for changing the setting f the driver body 42, and the processing of this flow chart is completed.

0082As described above, in the portable terminal device according to the present embodiment, in order to continuously and stably operating the input/output hardware 15a to 15c even if the setting or set value of the link information 32 is changed, input/output function requested by the application programs 21a to 21c is not executed when the remaining quantity of the battery 14 is not sufficient (step S42). Therefore, it is possible to avoid unstable operation of the input/output hardware 15a to 15c when the remaining quantity of the battery 14 is not sufficient.

0083In the portable terminal device according to the present embodiment, since link information 32 having lower priority order is sequentially released by the processing of "checking of battery remaining quantity" executed in accordance with interrupt from the timer 11a, it is possible to reduce the electricity consumption when the remaining quantity of the battery 14 is not enough.

0084Further, in the portable terminal device according to the present embodiment, value is registered in the electricity consumption value table 33 and the link information 32 is set using the function of the operating system 20, and the operating system 20 controls the input/output based on the registered content in the electricity consumption value table 33 and the set link information 32. Therefore, even if the input/output hardware is changed or added, it is possible to cope with this without changing the operating system 20 if a corresponding driver is added.

0085Further, in the portable terminal device according to the present embodiment, when the electricity consumption of the input/output hardware 15a to 15c is changed by setting value, even if there is not a sufficient remainder of the battery 14 for continuously and stably operating the input/output hardware 15a to 15c with the initial setting, it is possible to operate the input/output hardware 15a to 15c by changing the setting value. Therefore, it is possible to allow the input/output hardware to operate as much as possible.

0086In the above embodiment, the electricity consumption value of the input/output hardware 15a to 15c registered in the electricity consumption value table 33 is written in the corresponding drivers 21a to 21c as electricity consumption value data 44, 44a to 44n. As shown in <figref idref="f0009">Fig.9</figref>, an electricity consumption measuring instrument 18 may be added to the structure in <figref idref="f0002">Fig.2</figref>, and an electricity consumption value actually measured by this electricity consumption measuring instrument 18 may be registered in the electricity consumption value table 33. With this feature, even when the electricity consumption value table is not previously written in the drivers 21a to 21c, it is possible to cope with a variation in electricity consumption due to variation of characteristics of parts, or new compatible parts (such as PC card modem) which is announced after the registration to the drivers 21a to 21c.

0087In the above embodiment, the processing shown in the flow chart in <figref idref="f0006">Fig.6</figref> is executed in accordance with the interruption from the timer 11a in the CPU 11. This processing in the flow chart may be executed when the portable terminal device is turned ON.

0088The above embodiment has been described while taking the case where the entire portable terminal device is driven by electricity supplied from the battery 14. However, the present invention can be applied to a case where only the input/output hardware is driven by a battery. In this case, battery remaining quantity measuring means may be provided such as to correspond to the input/output hardware, and when a function of the requested input/output utilizes the input/output hardware which is driven by the battery, the same processing as described above may be carried out.

0089Although the above embodiment has been described while taking the case where the present invention is applied to the portable terminal device, the present invention can be applied to any types of information terminal devices which are driven by batteries (business power source supplied from electric power company may be used together) and which drive the input/output hardware.

0090In the above embodiment, the operating system 20 and programs of the drivers 21a to 21c which realize the function of the present invention are stored in the ROM 12. However, these programs may be stored in a floppy disk or CD-ROM and supplied, as may be installed in a hard disk provided in the portable terminal device for example. Alternatively, these programs may be stored and supplied in a ROM card which is designed to be detachably inserted to the portable terminal.