week 13 - IAS computer Flashcards
stored memory consept
a computer that can store program instructions electronically or optically rather than stored on it being stored on plug boards (that have to be rewired)
IAS structure
-main memeory
-ALU
-control unit
-I/O
Registers
Registers are fast, expensive memory built into the CPU for fast memory access; they are used to store data that is needed in the program execution.
Types of Registers
- Memory buffer register (MBR)
- Memory adress register (MAR)
- Instruction register (IR)
- Instuction buffer register (IBR)
-Program counter (PC) - Accumulator (AC)
- Multiplier Quotient (MQ)
MBR
Contains a word to be stored in memory or sent to I/O unit or receive a word from memory or I/O unit
MAR
Specifies the addresses in memory of the word to written to or read from
IR
Contains 8 bit opcode instructions
IBR
Temporarily holds the right hand instruction of a word in memory
PC
Contains the memory address of the next instruction to be fetched from memory
AC and MQ
Temporarily holds the operands and results of ALU operations
Instruction cycle
-Fetch - CPU fetches the instruction from main memory into the registers then decodes the instruction
-Execute - CPU executes the instruction fetched in the fetch cycle
IAS Computer 3 main concepts
- Single read–write memory (Data and Instructions)
- Addressable Memory
- Execution occurs in a sequential fashion (unless explicitly modified) from one instruction to the next.
Hardwired program
when you need to rewire the computer in order to process the data in the desired way or example the Adder subtractor
software program
When you build a general purpose configuration components that can perform various tasks and functions depending on control signals applied to the hardware. This means that you don’t have to rewire the hardware everytime you want to program the computer.
control signals
Control signals are essentially instructions that the computer interprets to an arithmetic or logical operation.
