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Intro to assembly language
1) The document discusses different levels of programming languages including machine language, assembly language, and high-level languages. Assembly language uses symbolic instructions that directly correspond to machine language instructions. 2) It describes the components of the Intel 8086 processor including its 16-bit registers like the accumulator, base, count, and data registers as well as its segment, pointer, index, and status flag registers. 3) Binary numbers can be represented in signed magnitude, one's complement, or two's complement form. Two's complement is commonly used in modern computers as it allows for efficient addition and subtraction of binary numbers.
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Intro to assembly language
- 1. Intro to Assembly Language MUHAMMADTASNIM MOHIUDDIN LECTURER, CSE, UIU 1
- 2. Levels of ProgrammingLanguages 1) Machine Language 2) Assembly Language (Low Level Language) 3) High Level Languages 2
- 3. Machine Language Setof fundamental instructions Native to a processor: executed directly by hardware Expressed as a pattern of 1’s and 0’s Here’s what a program-fragment looks like: 10100001 10111100 10010011 00000100 00001000 00000011 00000101 11000000 10010011 00000100 00001000 10100011 11000000 10010100 00000100 00001000 It means: z = x + y; 3
- 4. Assembly Language Onestep up from machine language Designed for a specific family of processors (different processor groups/family has different Assembly Language) Consists of symbolic instructions directly related to machine language instructions one-for-one and are assembled into machine language. Alphanumeric equivalent of machine language Mnemonics more human-oriented than 1’s and 0’s Example: for A = A + 4 MOV AX, A ADD AX, 4 MOV A, AX 4
- 5. High Level Languages Similar to Natural language. Designed to eliminate the technicalities of a particular computer. Statements compiled in a high level language typically generate many low- level instructions. Example: C, Java, Python etc 5
- 6. Advantages of High-LevelLanguages Program development is faster High-level statements: fewer instructions to code Program maintenance is easier For the same above reasons Programs are portable 6
- 7. Why Assembly Language? Accessibility to system hardware Assembly Language is useful for implementing system software Also useful for small embedded system applications Faster and shorter programs. Compilers do not always generate optimum code. Resident programs (that reside in memory while other program execute) and interrupt service routines (that handle input and output) are almost always develop in Assembly Language. Instruction set knowledge is important for machine designers. Compiler writers must be familiar with details of machine language. 7
- 8. Advantages of AssemblyLanguage Shows how program interfaces with the processor, operating system, and BIOS. Shows how data is represented and stored in memory and on external devices. Clarifies how processor accesses and executes instructions and how instructions access and process data. 8
- 9. Assembler An assembleris a program that converts source-code programs written in assembly language into object files in machine language Popular assemblers have emerged over the years for the Intel family of processors. These include … TASM (Turbo Assembler from Borland) NASM (Netwide Assembler for both Windows and Linux), and GNU assembler distributed by the free software foundation 9
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- 12. Computer Architecture Control Bus CPUMemory I/O Address Bus Data Bus 12
- 13. Organization of 8086Processor 16 bit Processor 16 bit data bus 16 bit registers 20 bit Address bus 13
- 14. Organization of 8086Processor CPU Memory Address Bus Data Bus 20 16 CPU-Memory Interface 16-bit Control Bus 14
- 15. Bytes and Words Information processed by computer is stored in its memory A memory element can store one bit of data Group of 8 bits forms one byte Group of 16 bits or 2 bytes forms one word 15
- 16. RAM and ROM Random-Access Memory (RAM) Can be performed read and write operation Program instruction and data are loaded into RAM Contents are lost when the machine is turned off ROM (Read-Only-Memory) Once initialized can’t be changed, can only be read Retain values event the machine is turned off Hence used to store system programs 16
- 17. Address Space of8086 17
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- 19. Number System • Consistsof TWO Things: – A BASE or RADIX Value – A SET of DIGITS • Digits are symbols representing all values less than the radix value. • Example is the Common Decimal System: – RADIX (BASE) = 10 – Digit Set = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9} 19
- 20. Decimal Number Systems Consider: 5032.21 210123 10 )10(1)10(2)10(2)10(3)10(0)10(5 01.02.023005000)21.5032( 5032.21 20
- 21. Commonly Occurring Bases •Binary – Radix = (2)10 – Digit Set = {0,1} • Octal – Radix = (8)10 – Digit Set = {0,1,2,3,4,5,6,7} • Hexadecimal – Radix = (16)10 – Digit Set = {0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F} 21
- 22. Any Base toDecimal A number with radix r is represented by a string of digits: An - 1An - 2 … A1A0 . A- 1 A- 2 … A- m 1 A- m The string of digits represents the power series: (Number)r = j = - 1 j j i i = 0 i rArA (Integer Portion) + (Fractional Portion) i = n - 1 j = - m 22
- 23. Hexadecimal 16-base numbersystem 16 symbols (0—9, A, B, C, D, E, F) Again radix is power of 2 4 bits to represent a hexadecimal number 23
- 24. Hexadecimal to Binary Restatethe hexadecimal as four binary digits starting at the radix point and going both ways. 24
- 25. Binary to Hexadecimal Groupthe binary digits into four bits groups starting at the radix point and going both ways, padding with zeros as needed in the fractional part. Convert each group of three bits to an hexadecimal digit. 25
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- 27. Binary Negative Numbers •In decimal we are quite familiar with placing a “-” sign in front of a number to denote that it is negative • But for binary numbers a computer won’t understand that • What happens in memory then? 27
- 28. Binary Negative Numbers Thereare several representations - Signed magnitude - One’s complement - Two’s complement 28
- 29. Signed Magnitude Leftbit (MSB) used as the sign bit 29
- 30. One’s Complement Invertthe ones and zeros 30
- 31. Subtraction with One'sComplement Steps for subtracting x from y with an n-bit 1's complement representation: Negate x using 1's complement. Add -x and y. If the sum exceeds n bits, add the extra bit to the result. If the sum does not exceed n bits, leave the result as it is. The result will be in 1's complement form 31
- 32. Example: subtracting 1from 7 using 1's complement First, we need to convert 0001 to its negative equivalent in 1's complement. Next we perform addition of 7 and our computed 1's complement of -1. Notice that our addition caused an overflow bit. Whenever we have an overflow bit in 1's complement, we add this bit to our sum to get the correct answer. If there is no overflow bit, then we leave the sum as it is. 32
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- 34. Two’s Complement Take 1’scomplement then add 1 OR Toggle all bits to the left of the first ‘1’ from the right Example: 0 1 0 1 0 0 0 0 1 0 1 1 0 0 0 0 0 1 0 0 1 1 1 1 + 1 1 0 1 1 0 0 0 0 00001010 34
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- 36. Subtraction with Two’sComplement Steps for subtracting x from y with an n-bit 2's complement representation: Negate x using 2's complement. Reverse all the bits in x. Add 1 to form -x. Add -x and y. Discard any bits greater than n. The result will be in 2's complement form 36
- 37. Example: subtracting 1from 7 using 2's complement First, we need to convert 00012 to its negative equivalent in 2's complement. Next we perform addition of 7 and our computed 2's complement of -1. Notice that our addition caused an overflow bit. Whenever we have an overflow bit in 2's complement, we discard the extra bit. This gives us a final answer of 01102 (or 610) 37
- 38. Another Example 1-7 = 1 + (-7) 0001 +1001 1010 2’s complement of -7 1010 is the 2’s complement of -6 38
- 39. Registers of 8086 Intel8086 contains following registers: General Purpose Registers Pointer and Index Registers Segment Registers Instruction Pointer Status Flags 39
- 40. General Purpose Registers Thereare four 16-bit general purpose registers: Accumulator Register (AX) Base Register (BX) Count Register (CX) Data Register (DX) 40
- 41. Following four 16-bitregisters are under this category: Stack Pointer (SP) Base Pointer (BP) Source Index (SI) Destination Index (DI). Pointer & Index Register 41
- 42. Segment Register There arefour 16-bit segment registers in Intel 8086: Code Segment Register (CS), Data Segment Register (DS), Stack Segment Register (SS), Extra Segment Register (ES). 42
- 43. Rest 2 Registers InstructionPointer Status Flag Register 43