Computer Organization - Programming the basic computer : Machine Language, Assembly Language and Assembler
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The document outlines fundamental concepts in computer programming, focusing on machine language, assembly language, and the structure of assemblers. It details various programming languages, the instruction set for a basic computer, and the process of converting symbolic programs into binary code through assembly. The document also explains the dual-pass method of assemblers to translate code and illustrates with examples of programming in binary, hexadecimal, and symbolic formats.
Computer Organization - Programming the basic computer : Machine Language, Assembly Language and Assembler
- 1. GANDHINAGAR INSTITUTE OF TECHNOLOGY Computer Engineering Department Computer Organization(2140707) Programming the basic computer : Machine language, Assembly language, Assembler and passes of assembler. PREPARED BY: Maitri Thakkar9150120107064) GUIDED BY: Prof. Raxit Jani
- 2. INTRODUCTION ļ¢ A computer system includes both hardware and software. The designer should be familiar with both of them. ļ¢ This chapter introduces some basic programming concepts and shows their relation to the hardware representation of instructions. ļ¢ A program may be : dependent or independent on the computer that runs it.
- 3. MACHINE LANGUAGE ļ¢ Program: A list of instructions that direct the computer to perform a data processing task. ļ¢ There are many programming languages (C++, JAVA). However, the computer executes programs when they are represented internally in binary form. ļ¢ Categories of Programs: ļ Machine Language: ā¢ Binary Code ā¢ Octal or hexadecimal code ļ Assembly Language: ā¢ Symbolic code ļ High level programming languages
- 4. INSTRUCTION SET OF THE BASIC COMPUTER: Symbol Hex code Description ļ AND 0 or 8 AND M to AC ļ ADD 1 or 9 Add M to AC, carry to E ļ LDA 2 or A Load AC from M ļ STA 3 or B Store AC in M ļ BUN 4 or C Branch unconditionally to m ļ BSA 5 or D Save return address in m and branch to m+1 ļ ISZ 6 or E Increment M and skip if zero ļ CLA 7800 Clear AC ļ CLE 7400 Clear E ļ CMA 7200 Complement AC ļ CME 7100 Complement E ļ CIR 7080 Circulate right E and AC ļ CIL 7040 Circulate left E and AC ļ INC 7020 Increment AC, carry to E ļ SPA 7010 Skip if AC is positive ļ SNA 7008 Skip if AC is negative ļ SZA 7004 Skip if AC is zero ļ SZE 7002 Skip if E is zero ļ HLT 7001 Halt computer ļ INP F800 Input information and clear flag ļ OUT F400 Output information and clear flag ļ SKI F200 Skip if input flag is on ļ SKO F100 Skip if output flag is on ļ ION F080 Turn interrupt on ļ IOF F040 Turn interrupt off Here, m: effective address M: memory word (operand) found at m.
- 5. BINARY PROGRAM TO ADD TWO NUMBERS: Location Instruction Code 0 0010 0000 0000 0100 1 0001 0000 0000 0101 10 0011 0000 0000 0110 11 0111 0000 0000 0001 100 0000 0000 0101 0011 101 1111 1111 1110 1001 110 0000 0000 0000 0000 HEXADECIMAL PROGRAM TO ADD TWO NUMBERS: Location Instruction 000 2004 001 1005 002 3006 003 7001 004 0053 005 FFE9 006 0000 PROGRAM WITH SYMBOLIC OPCODE: Location Instruction Comments 000 LDA 004 Load 1st operand into 001 ADD 005 Add 2nd operand to AC 002 STA 006 Store sum in location 0 003 HLT Halt computer 004 0053 1st operand 005 FFE9 2nd operand (negative) 006 0000 Store sum here FORTRAN PROGRAM: INTEGER A, B, C DATA A,83 / B,-23 C = A + B END
- 6. ASSEMBLY LEVEL LANGUAGE ļ¢ The symbolic program(contains letters, numerals or special characters) is referred to as an assembly language program. ļ¢ The basic unit of an assembly language program is a line of code. ļ¢ Each line of assembly language program is arranged in three columns called fields: ļ The label field may be empty or it may contain a symbolic address of up to 3 characters. ļ The instruction field specifies a machine instruction or a pseudo instruction. ļ The comment field may be empty or it may include a comment.
- 7. INSTRUCTION FIELD: ļ¢ Instruction field in an assembly level language may specify one of the following three items: ļ A memory-reference instruction(MRI) : MRI consist of two or three symbols separated by spaces. ļ¢ ADD OPR (direct address MRI) ļ¢ ADD PTR I (indirect address MRI) ļ A register-reference or input-output instruction(Non- MRI) : Non MRI instructions do not have an address part. ļ Pseudo instruction with or without operand : Symbolic address used in the instruction field must be defined somewhere as a label.
- 8. PSEUDO INSTRUCTION: ļ¢ Pseudo instruction is not a machine instruction but rather an instruction to the assembler giving information about some phase of translation. ļ¢ Four pseudo instructions that are recognized by an assembler are: ļ ORG N : Hexadecimal number N is the memory loc. for the instruction or operand listed in the following line. ļ END : Denotes the end of symbolic program. ļ DEC N : Signed decimal number N to be converted to binary. ļ HEX N : Hexadecimal number N to be converted to binary.
- 9. ASSEMBLER: ļ¢ An assembler is a program that accepts a symbolic language program and produces its binary machine language equivalent. ļ¢ The input symbolic program is called the source program and the output binary program is called the output program. ļ¢ The assembler is a program that operates on character strings and produces an equivalent binary interpretation.
- 10. FIRST PASS OF AN ASSEMBLER: ļ¢ During the first pass, the assembler generates a table that corelates all user- defined address symbols with their binary equivalent value. LC := 0 Scan next line of code Set LC Label no yes yes no ORG Store symbol in address- symbol table together with value of LC END Increment LC Go to second pass no yes
- 11. SECOND PASS : Second pass LC <- 0 Scan next line of code Set LC yes yes ORGPseudo instr. yes END no Done yes MRI no Valid non-MRI instr. no Convert operand to binary and store in location given by LC no DEC or HEX Error in line of code Store binary equivalent of instruction in location given by LC yes no Get operation code and set bits 2-4 Search address- symbol table for binary equivalent of symbol address and set bits 5-16 I Set first bit to 0 Set first bit to 1 yes no Assemble all parts of binary instruction and store in location given by LC Increment LC The binary Translation is done during the second pass.