Chapter 1 Background

1. Chapter 1 Background System Software Chih-Shun Hsu http://cc.shu.edu.tw/~cshsu

2. Introduction • System software consists of a variety of programs that support the operation of a computer • By understanding the system software, you will gain a deeper understanding of how computers actually work • One characteristic in which most system software differs from application software is machine dependency

3. System programs • Text editor: create and modify the program • Compiler: translate programs into machine language • Loader and linker: load the resulting machine language program in to memory and prepared for execution • Debugger: help detect errors in the program • Assembler and macro processor: translate program written in assembly language into machine language • Operating system: control all processes and take care of all the machine-level details

4. SIC Machine Architecture(1/2) • Simplified Instructional Computer (SIC) comes in two versions: the standard model and an XE (extra equipment) version • 3 consecutive bytes form a word • Total 32768 (215) bytes in the memory • Registers: • A: Accumulator • X: Index register • L: Linkage register • PC: Program counter • SW: Status word

5. SIC Machine Architecture(2/2) • Data format: 24-bit binary numbers; negative values: 2’s complement • Instruction format: • Address mode: • Direct x=0 TA=address • Indexed x=1 TA=address+(X) • Instruction set: load and store registers, integer arithmetic operations, compare instruction, conditional jump instructions, subroutine linkage • Input, output: read data (RD) or write data (WD)

6. SIC/XE Machine Architecture(1/3) • Memory: I megabyte (220 bytes) • Registers • B: base register • S, T: General working register • F: Floating-point accumulator (48 bits) • Data format: 48-bit floating-point type, f*2(e-1024)

7. SIC/XE Machine Architecture(2/3) • Instruction formats • Format 1 • Format 2 • Format 3(e=0) • Format 4(e=1)

8. SIC/XE Machine Architecture(3/3) • Addressing mode • Base relative b=1,p=0 TA=(B)+disp • Program-counter b=0,p=1 TA=(PC)+disp • Instruction set: load and store new registers, floating-point arithmetic operations, register-to-register arithmetic operations, supervisor call instruction

9. Addressing Mode • Direct addressing: b=0, p=0, disp in a format 3 instruction is the target address • Indexed addressing: x=1, can be combined with any addressing mode • Immediate addressing: i=1, n=0, target address is used as the operand • Indirect addressing: i=0, n=1, the value of the word at the target address is taken as the address of the operand value • Simple addressing: i=n=0 or 1, the target address is taken as the location of the operand

10. Examples of SIC/XE addressing mode

11. Data movement operations (SIC)

12. Data movement operations (SIC/XE) #: immediate addressing

13. Arithmetic operations (SIC) BETA=ALPHA+INCR-1 DELTA=GAMMA+INCR-1

14. Arithmetic operations (SIC/XE)

15. Looping and indexing operations (SIC) for (int i=0; i<11; i++) STR2[i]=STR1[i]

16. Looping and indexing operations (SIC/XE)

17. Indexing and looping (SIC) for (int i=0; i<300; i+=3) GAMMA[i/3]=ALPHA[i/3]+BETA[i/3]

18. Indexing and looping (SIC/XE)

19. scanf(“%c”,&DATA) printf(“%c”,DATA) Input and output operations

20. for (int i=0; i<100; i++) scanf(“%c”,&RECORD[i]); Subroutine call and record input operations (SIC)

21. Subroutine call and record input operations (SIC/XE)

22. CISC and RISC machines • Complex instruction set computers (CISC): VAX, Pentium Pro • Reduced instruction set computers (RISC): UltraSPARC, PowerPC, Cray T3E

23. Pentium Pro Architecture • An address consists of two parts-- a segment number and an offset that points to a byte within the segment • Registers: eight general purpose registers: EAX, EBX, ECX, EDX, ESI, EDI, EBP, and ESP, special purpose registers: EIP, FLAGS, CS, SS DS, ES, FS, and GS • Data format: the least significant part of a numeric value is stored at the lowest-numbered address (called little-endian) • Instruction format: 1 byte to 10 bytes • 400 machine instructions

24. PowerPC Architecture • Virtual address space of 264 bytes • Address space is divided into fixed-length segments, which are 256 megabytes long • Each segment is divided in to pages, which are 4096 bytes long • 32 general purpose registers (64 bits long) • Data format: the most significant part of a numeric value is stored at the lowest-numbered address (called big-endian) • Seven basic instruction format (32 bits long) • Approximately 200 machine instructions