CS401 Computer Architecture and Assembly Language Programming

Assembly 1-5 lectures

1. The address bus is unidirectional and address always travels from processor to memory.
2. Data moves from both, processor to memory and memory to processor, so the data bus is bidirectional.
3. A memory cell is an n-bit location to store data, normally 8-bit also called a byte. The number of bits in a cell is called the cell width.
4. The memory cell cannot be wider than the width of the data bus.
5. Memory changes its behavior in response to this signal from the processor.
6. Operands are the data on which we want to perform a certain operation.
7. There are temporary storage places inside the processor called registers.
8. Registers are relatively very small in number, and are therefore a very scarce and precious resource.
9. There is a central register in every processor called the accumulator.
10. Traditionally all mathematical and logical operations are performed on the accumulator.
11. A 32bit processor has an accumulator of 32 bits.
12. The bits of the accumulator work in parallel as a unit and each bit mean the same thing. The bits of the flags register work independently and individually, and combined its value is meaningless.
13. The program counter holds the address of the next instruction to be executed is called instruction pointer.
14. Just this one number tells it that it has to add, where its operands are, and where to store the result. This number is called the opcode.
15. The dumb translator that will convert these mnemonics back to the original opcodes is a key program to be used throughout this course and is called the assembler.
16. These instructions are used to move data from one place to another is called Data Movement Instructions
17. Technically iAPX88 stands for “Intel Advanced Processor Extensions 88.”
18. 8088 is a 16bit processor with its accumulator and all registers of 16 bits.
19. The architecture of a processor means the organization and functionality of the registers it contains and the instructions that are valid on the processor.
20. Intel introduced the first 16bit processor named 8088 at a time when the concept of personal computer was evolving.
21. The A of AX stands for Accumulator.
22. The B of BX stands for Base because of its role in memory Addressing
23. The C of CX stands for Counter as there are certain instructions that work with an automatic count in the CX register.
24. The D of DX stands for Destination as it acts as the destination in I/O operations. SI and DI stand for source index and destination index respectively.
25. This is the special register containing the address of the next instruction to be executed. No mathematics or memory access can be done through this register is called Instruction Pointer (IP)
26. It is a memory pointer and is used indirectly by a set of instructions is called Stack Pointer (SP).
27. Program is an ordered set of instructions for the processor.
28. An implied operand means that it is always in a particular register say the accumulator, and it need not be mentioned in the instruction.
29. To start a comment a semicolon is used and the assembler ignores everything else on the same line.