Welcome to Systems SoftwareSlide 2ConcernedApplication ProgramsSystems ProgramsAssembler Program - SIC (Intermediate Code)Assembler Program – SIC/XE (Intermediate Code)SIC / SICXECHARACTERISTICS OFSIC Architecture - MemorySIC Architecture - RegistersRegister Names and Usage - SICData Formats - SICData Formats ExampleInstruction Formats - SICAddressing Modes - SICInstruction Set - SICInput/Output - SICSlide 19SIC/XE Architecture - MemorySIC/XE Architecture - RegistersRegister Names and Usage – SIC and SIC/XEFOUR Additional Registers and their Usage SIC/XEData Formats – SIC/XESlide 25Floating Point Format SIC/XEFloating Point (cont) SIC/XESlide 28Slide 29Slide 30Instruction Formats – SIC/XESlide 32Addressing Modes – SIC/XE Format 3/4 InstructionAddressing Modes – SIC/XE Format 3/4 Instruction (cont)Addressing Modes – SIC/XE Format 3/4 Instruction the disp (cont)Instruction Set – SIC/XEInput/Output – SIC/XESummary Addressing ModesSlide 39Slide 40Slide 41Welcome to Systems SoftwareThe purpose of this course is to provide background in fundamental types of system software, particularly assemblers, loaders, macro processors, and linkage editors.The course uses a simplified instructional computer (SIC and SIC/XE) to illustrate machine level system software requirements.Welcome to Systems SoftwareA major objective of the course will be for students to design and implement a working (cross) assembler for SIC and part of SIC/XE.ConcernedApplication programs–Machine independent–Solves a specific problemSystems programs–Machine dependent–Support computers operationCompilerAssemblerLinkerLoaderOSApplication ProgramsC/C++, Java, Perl, Python, Fortran, PL/1, LISP, Prolog, Pascal, C#, RubyPrograms to sort, search, etc.Systems ProgramsCompiler–Translates application programs to intermediate codeAssemblers–Translates intermediate code to machine codeLinkers–Links the machine code modules into oneLoaders–Loads the machine code in memoryOS–Controls the operation of the computerAssembler Program - SIC (Intermediate Code)LDA FIVE Load 5 into ASTA ALPHA Store in ALPHALDCH CHARZ Load character ‘Z’ into ASTCH C1 Store in C1 . .ALPHA RESW 1 one word variableFIVE WORD 5 one word constantCHARZ BYTE C’Z’ one byte constantC1 RESB 1 one byte variableAssembler Program – SIC/XE (Intermediate Code)LDA #5 Load 5 into ASTAALPHA Store in ALPHALDCH #90 Load character ‘Z’ into ASTCH C1 Store in C1 . .ALPHA RESW1 one word variableC1 RESB 1 one byte variableSIC / SICXESimple Instruction ComputerSimple Instruction Computer ExtendedDesigned to be similar to real computersDesigned to avoid unnecessary detailCHARACTERISTICS OF SICSIC Architecture - MemoryBytes – 8 bitsWord – 3 bytes (24 bits)Byte addressable Words addressed by lowest byte32767 (215) bytes of total memorySIC Architecture - Registers5 registers Each a full wordEach special purposeRegister Names and Usage - SICA 0 Accumulator; used for arithmeticX 1 Index register; used for addressingL 2 Linkage resister; used for return addressPC 8 Program counter; address of next inst.SW 9 Status word; variety of information including a condition code (CC)Data Formats - SICIntegers – 24 bit binary 2’s complementCharacters – 8 bit ASCIINo floating pointData Formats ExampleInteger 5 000000000000000000000101-5 111111111111111111111011Character A 01000001 R 01010010Instruction Formats - SIC24 bit 8 bit opcode 1 bit addressing mode 15 bit addressAddressing Modes - SICDirect x = 0 Target address = addressIndexed x = 1 Target address + (X) (X) is the contents of register XInstruction Set - SICLoad and Store Registers–LDA, LDX, STA, STX, etc.Integer Arithmetic (all involve register A)–Add, SUB, MUL, DIVCompare–COMP – compares A with a word in memory–Sets the CC in the SWJump instructions–JLT, JEQ, JGT – based on the CC as set by COMPSubroutine Linkage–JSUB – jumps to subroutine, places return address in L–RSUB – returns, using the address in LInput/Output - SICTD – test device is ready to send/receive data–CC of < means device is ready–CC of = means device is not readyRD – read data, when the device is readyWD – write dataTransfers 1 byte at a time to or from the rightmost 8 bits of register A.Each device has a unique 8-bit code as an operand.CHARACTERISTICS OF SIC/XESIC/XE Architecture - MemoryBytes – 8 bitsWord – 3 bytes (24 bits)Byte addressable Words addressed by lowest byte1 meg (220) bytes of total memory (more memory leads to a change in instruction formats and addressing modesSIC/XE Architecture - Registers5 registers of SIC + 4 additionalEach a full wordEach special purposeRegister Names and Usage – SIC and SIC/XEA 0 Accumulator; used for arithmeticX 1 Index register; used for addressingL 2 Linkage resister; used for return addressPC 8 Program counter; address of next inst.SW 9 Status word; variety of information including a condition code (CC)FOUR Additional Registers and their Usage SIC/XEB 3 Base register, used for addressingS 4 General register – no special useT 5 General register – no special useF 6 Floating-point accumulator (48 bits)Data Formats – SIC/XEIntegers – 24 bit binary 2’s complementCharacters – 8 bit ASCIIFloating point – 48 bit floating pointData Formats – SIC/XE24 bit integer48 bit floating point1 bit sign 11 bit exponent 36 bit fractionFloating Point Format SIC/XEFraction is a value between 0 and 1The binary point is immediately before the high order bit which must be 1The exponent is an unsigned binary number between 0 and 2047Floating Point (cont) SIC/XESuppose the exponent is e and the fraction is fThe number is f * 2 (e+1024)0 sign is positive1 is negative0 is all bits including sign are 0Data Formats ExampleInteger 5 = 000000000000000000000101-5 = 111111111111111111111011Character A 01000001Data Formats ExampleFloat 4.89 = .100111000111101011100001010001111010111000010100 * 23 (1027)=0 10000000011 100111000111101011 100001010001111010Data Formats ExampleFloat -.000489 =