1. Chapter 2: Data Manipulation

2. Chapter 2: Data Manipulation
2.1 Computer Architecture
2.2 Machine Language
2.3 Program Execution

3. Computer Architecture
Central Processing Unit (CPU) or processor
Arithmetic/Logic unit versus Control unit
Registers : temporary storage units within the CPU that hold data being processed and are very easily accessible by CPU. Two types of Registers
General purpose : Can be used for any task
Special purpose : Used for special task e.g Program Counter ( PC) and Instruction Register (IR)
Bus
Motherboard

4. Inside the System Unit

6. Figure 2.1 CPU and main memory connected via a bus

7. Bus and its types
A bus connects parts of the CPU to one another. It also links the CPU to the various components of the system board.
There are three types of buses:
Data Bus
Address Bus
Control Bus

8. Von Neumann Stored Program Concept
A program can be encoded as bit patterns and stored in main memory. From there, the CPU can then extract the instructions and execute them. In turn, the program to be executed can be altered easily.

9. Terminology
Machine instruction: An instruction (or command) encoded as a bit pattern recognizable by the CPU
Machine language: The set of all instructions recognized by a machine

10. Machine Instruction Types
Data Transfer: copy data from one location to another
Arithmetic/Logic: use existing bit patterns to compute a new bit patterns
Control: direct the execution of the program

11. Data Transfer Instructions
Load : To fetch data from Main Memory
Store : To save data into Main Memory
Move: To transfer data from register to register

12. Arithmetic / Logical Instructions
Add / Sub / Mult / Div / Mod
And / OR / XOR / NOT /SHIFT /ROTATE

13. Arithmetic/Logic Operations
Logic: AND, OR, XOR
Masking
Rotate and Shift: circular shift, logical shift, arithmetic shift
Arithmetic: add, subtract, multiply, divide
Precise action depends on how the values are encoded (two’s complement versus floating-point).

14. Control Instructions
Jump
Halt

15. What is a High Level Language and Machine Language
A High Level Language is easily understood by human beings
A Machine Language Instruction is in Binary format easily understood by the Machine / Computer
Difference ??
One High Level Language Instruction gets translated into Many Machine Level Instructions thus taking more time to execute

16. Example If I write in High Level Language a:= b+c
It gets translated into 4 machine level instructions:
Fetch b
Fetch c
Add b and c
Store their result in a

17. Figure 2.2 Adding values stored in memory

18. Figure 2.4 The architecture of the machine described in Appendix C

19. Difference Between PC and IR
Program counter (PC) :
It contains the address of the next instruction to be executed
Instruction Register:
It contains the Instruction that is currently being executed by the CPU

20. Parts of a Machine Instruction
Op-code: Specifies which operation to execute
Operand: Gives more detailed information about the operation
Interpretation of operand varies depending on op-code

21. Figure 2.5 The composition of an instruction for the machine in Appendix C

22. Figure 2.6 Decoding the instruction 35A7

23. Figure 2.7 An encoded version of the instructions in Figure 2.2

24. Program Execution Controlled by two special-purpose registers
Program counter: address of next instruction
Instruction register: current instruction
Machine Cycle
Fetch
Decode
Execute

25. Figure 2.8 The machine cycle

26. Figure 2.9 Decoding the instruction B258

27. Figure 2. 10 The program from Figure 2
Figure The program from Figure 2.7 stored in main memory ready for execution

28. Figure 2.11 Performing the fetch step of the machine cycle

29. Figure 2.11 Performing the fetch step of the machine cycle (cont’d)