Conventional memory

1. Conventional Memory

2. The memory system is divided into three main parts. They are:- 1. TPA (Transient Program Area) 2. System Area 3. XMS (Extended Memory System) Memory System

3. The first 1 M byte of memory is called the real memory or conventional memory . It is called so because each microprocessor is designed to function in this area by using the real mode of operation. What is conventional memory?

4. The conventional memory of 1 M byte is comprised of two portions. They are:- TPA – 640k System Area – 384k Cont..

5. The Transient program area holds the dos operating system and other programs that control the computer system. The TPA also stores any currently active or inactive DOS application programs. The size of TPA is 640KB. DOS requires a portion of TPA to function. TPA

6. Both PCDOS and MSDOS are compatible with TPA. Windows and OS/2 are other two operating systems that are compatible with DOS programs and executes it. Cont…

7. Interrupt vectors access various features of the DOS, BIOS and applications. System BIOS is a collection of programs stored in ROM or Flash Memory. Interrupt Vectors

8. Contains the transient data used by the program to access I/O devices and internal features of the computer system. These are stored in the TPA so they can be changed as the system operates. BIOS and DOS communication area

9. It is a program that loads into TPA whenever the MSDOS or PCDOS system is started. This program allow DOS to use keyboard, printer, video display and other I/O devices often found in computer system. IO.SYS

10. The size of driver area and number of drivers changes from one system to another. Drivers are programs that control installable I/O devices. Drivers are files normally they have extension .SYS and sometimes it will be .EXE. REGEDIT is a program that contains information about system and the drivers. Device drivers

11. Controls the operation of the computer when keyboard is operated in DOS mode. Incase if it is erased the computer cannot be used with keyboard in DOS mode. COMMAND.COM

12. This area holds DOS application programs as they are executed. This application includes word processor and spreadsheets. Also it holds TSR (terminate and stay resident) programs that remain in memory in an inactive state until activated by interrupt. Free TPA

13. It occupies 2 area of memory. One area of 16 bytes of memory at the top and another large area of memory located near the bottom of TPA. Size depends on version of DOS installed. If DOS is installed in High Memory, most of the TPA is free to hold Application program. MSDOS program

14. It is smaller than TPA and it is of 384 kb in size. It contains program on either a read only memory or flash memory and RAM for data storage. System Area

15. It is the first part in system area, it contains video control programs on ROM or flash memory. The size and amount of memory used depends on the type of video display adapter. The Video Display Ram is Classified into 3 parts:- Video RAM (Graphics) Video RAM (Text) Video BIOS ROM Video Display RAM

16. Video RAM (Graphics ) used to store graphical or bit-mapped data. Video RAM (Text area) stores Text. Video BIOS ROM contains program that control the DOS Video display.

17. C8000H – DFFFFH is free. This area is used for expanded memory systems. It allows a 64-k byte page frame of memory to be used by application programs. Free Area

18. The memory region between E0000H – EFFFFH contains the BASIC language on ROM found in early IBM personal computer systems. In newer systems this area is free and referred as upper memory, which is used as extra RAM for the use of DOS programs. BASIC Language ROM

19. It controls the operation of Basic I/O devices connected to the computer. The Video system is not controlled by this. I/O space in a computer system extends from 0000H to FFFFH which allows the microprocessor to communicate between itself and the outside world. BIOS ROM

20. This memory from 0000H to FFFFH is divided into two regions. 0000H to 03FFH is reserved for system devices and other for expansion on newer system that extends from I/O port 0400H through FFFFH.

21. Thank You.