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Chapter 2 Parts of a Computer System

Chapter 2 Parts of a Computer System. 2.1 PC Hardware: Memory. 80x86 Memory. Collection of “slots” each of which holds one byte (8 bits) Each slot identified by an address 32-bit systems use 32-bit addresses 64-bit systems use 64-bit addresses. Memory Units.

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Chapter 2 Parts of a Computer System

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  1. Chapter 2 Parts of a Computer System

  2. 2.1 PC Hardware: Memory

  3. 80x86 Memory • Collection of “slots” each of which holds one byte (8 bits) • Each slot identified by an address • 32-bit systems use 32-bit addresses • 64-bit systems use 64-bit addresses

  4. Memory Units • 1Kb = 210 = 1,024 (about a thousand), • 1Mb = 220 = 1,048,576 (about a million) • 1Gb = 230 = 1,073,741,824 (about a billion)

  5. 2.1 PC Hardware: The CPU

  6. CPU’s Function • Fetch instruction from memory • Decode instruction • Execute instruction • Store results

  7. 80x86 Registers • Internal to CPU – rapidly accessed • Used in arithmetic and other operations • 64-bit CPUs have larger and more registers

  8. General Registers, 32-bit CPUs • EAX, EBX, ECX, EDX, each 32 bits long • The low-order 16 bits can be referenced by AX, BX, CX and DX, respectively • The low-order 8 bits can be referenced by AL, BL, CL and DL, respectively • Bits 8-15 can be referenced by AH, BH, CH and CH, respectively • EAX is called the accumulator and sometimes has special instruction formats associated with it

  9. Index Registers • ESI, 32-bit source index used for • Source address in string moves • Array index • General purposes • EDI, 32-bit destination index used for • Address of destination in string moves • Array index • General purposes

  10. Stack Pointer, Base Pointer and Segment Registers • ESP, 32-bit stack pointer • Holds address of top of stack • EBP, 32-bit base pointer • Used in procedure calls to hold address of reference point in the stack • Segment Registers used in segmented memory model • CS, DS, ES, FS, SS, GS • Each 16 bits long holding a segment selector • Managed by the operating system with flat memory model programming

  11. Other Registers • EIP, 32-bit instruction pointer • Holds address of next instruction to be fetched for execution • EFLAGS, 32-bit • Collection of flags, or status bits • Records information about many operations • Carry Flag (CF) is bit 0 • Zero Flag (ZF) is bit 6 • Sign Flag (SF) is bit 7 • Overflow Flag (OF) is bit 11

  12. Registers in 64-bit CPUs • RAX, RBX, RCX, RDX, RSI, RDI, RSP, RBP, RIP, RFLAGS extend the 32-bit registers • Low-order 32 bits of RAX can be referenced by EAX; similarly for other registers • R8 – R15 are new 64-bit general-use registers • Low-order 32-bits of R8 can be referenced by R8D • Low-order 16 bits by R8W; 8 bits by R8B

  13. 2.3 PC Hardware: I/O Devices

  14. Input/Output • At the hardware level, I/O ports are used • 64K port addresses • Since the instructions that access ports are unavailable in ordinary application programming, I/O is typically done by calls to operating system routines

  15. 2.4 PC Software

  16. Operating System • Manages program execution • Provides access to I/O devices • Provide user interface • Command line interface (e.g., DOS) • Graphical user interface (e.g., Windows)

  17. Text Editors • Used to create source programs or data files • Notepad comes with Windows • Word processors add extra formatting information • not normally used for creating assembly language source files

  18. Language Translators • Interpreters translate each high-level language source code line every time it is needed for execution • Compilers translate HLL source code to object code that is almost ready for the CPU to execute • Assemblers translate assembly language – a low level language – to object code

  19. Linker • Object code files produced by a compiler or assembler are not quite ready for execution • A linker combines object code files and prepares them to be loaded into memory for execution

  20. Debugger • Allows the programmer to control execution of a program • Step through instructions one at a time • Stop at a preset breakpoint • Lets you look at memory or register contents • Helps find programming errors • Helps understand how the computer works

  21. Integrated Development Environment • Single interface provides access to text editor, compiler or assembler, linker and debugger • Microsoft Visual Studio is an IDE

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