Week 1 - Basic Computer Architecture Flashcards
What is a ‘bit’ exactly?
A bit is a binary digit (T/F, 1/0). It is a representation of a value. The significance varies depending on the current application.
What is a boolean operation?
Operations that manipulate bit values of True/False to obtain an output of True/False.
Explain an AND operation.
Looks at two statements & produces a true output only when both inputs are true.
Explain an OR operation.
Looks at two statements & produces a true output when any of the inputs are true.
Explain an XOR operation.
Looks at two statements & produces a true output only when one or the other input is true but not both.
Explain flip-flop logic.
It is a means of holding one bits state through the use of boolean logic. Two inputs, one output, one input sets the output to 1 and one input sets the output to 0.
What is the stored program concept and why was it a leap forward?
The store program concept says that the CPU can be wired to perform standard machine language instructions and the program itself can be stored in memory just like data. It meant that the program can simply be modified in memory rather than physically rewiring the CPU for each new program. Major time, flexibility and cost improvements.
Explain Von Neumann Architecture and why it can be a problem.
The Von Neumann architecture consists of a processing unit (CPU) connected to main memory and I/O controllers via a central bus. A bottleneck can occur when the CPU and I/O controllers are both trying to contact main memory at the same time.
Explain Direct Memory Access (DMA).
The ability of controllers to access main memory direct on the bus. Computing resources not wasted during slow data transfer. CPU can send controller instructions to read disk sector and put contents in memory then continue on with other tasks. Can lead to Von Neumann bottleneck.
Explain lossless vs lossy compression schemes
No information is lost during the compression process vs some information may be lost.
Machine instructions groupings
- Data transfer group – request the movement of data from one location to another
- Arithmatic/Logic group – request activity be performed within the ALU
- Control group – direct the execution of the program rather than manipulate data (stop, jump, branch)
Machine cycle and elements of machine instructions
- Fetch – retrieve the next instruction set from memory & increment program counter
- Decode – decode the bit pattern in the instruction register
- Execute – perform the action required by the instruction in the instruction register
CPU components
- Arithmetic/Logic Unit – performs operations on data (+/-, &, OR, XOR, NOT)
- Control Unit – Co-ordinates activities of computer CPU & hardware
- Register unit – contains general & special purpose registers for storing data being used in CPU.
Explain LSB & MSB
In a string of bits the LSB is the bit with the lowest value and MSB is the bit with the highest value. Typically envisaged as running left to right MSB to LSB
