Unit 2 - Computer Systems

Question 1

Advantages of using binary numbers

Answer 1

• Few rules for addition - making calculations simpler
• Degraded signal can still be detected (as representing 1)

Question 2

Each character on the keyboard has a unique binary code which is called…

Answer 2

ASCII

Question 3

What does ASCII include

Answer 3

• non printable chars (e.g <return>, <tab>, <delete>)</delete></tab></return>
• printable chars

Question 4

What are control characters

Answer 4

e.g RETURN, TAB, DELETE

(non printable characters)

Question 5

Unicode

Answer 5

Represents more chars with 16-bit character code (2^16) this can represent foreign languages like Arabic and Chinese

Question 6

ASCII advantage

Answer 6

1 char = 1 byte (less memory)

Question 7

ASCII disadvantage

Answer 7

only 255 possible chars

Question 8

Unicode advantage

Answer 8

2^16 possible chars (represents foreign langs.)

Question 9

Unicode disadvantage

Answer 9

1 char = 2 bytes (more memory)

Question 10

What is machine code

Answer 10

binary

Question 11

name the 2 translators

Answer 11

interpreter
compiler

Question 12

What is an interpreter

Answer 12

Converts and executes each line of code one line at a time

Question 13

Interpreter advantages

Answer 13

Immediately tells programmer when syntax error is made
Good for humans learning to program ^

Don’t need to leave programming env (e.g., vscode or livecode)

Question 14

Interpreter disadvantages

Answer 14

Needs to be translated every time the program is run

Question 15

Compiler

Answer 15

Will not run until entire code is turned into machine code

Question 16

Compiler advantages

Answer 16

Once translated, it doesn’t need to be translated again ∴ runs faster

Compiled code requires less memory to execute

Question 17

Compiler disadvantage

Answer 17

Compiled code cannot be edited

Question 18

What are the 3 parts of a CPU (processor)

Answer 18

• The control unit
• The arithmetic & logic unit (ALU)
• Registers

Question 19

What is the control unit for

Answer 19

• responsible for running programs that are loaded into main memory
• sends signals to fetch instructions from main memory
• understands these instructions
• carries out the instructions that are fetched from main memory

Question 20

What does the ALU do

Answer 20

Carries out computer’s arithmetical functions like addition, division etc
Also does logical functions like IF, AND, WHILE etc

Question 21

What are registers

Answer 21

Small temp memory locations locate. They store the data for the current instruction being processed.

Question 22

Main memory

Answer 22

either ram or rom

Question 23

Backing storage

Answer 23

outside the main processor, e.g SSDs, HDDs

Question 24

ROM - read only memory

Answer 24

• Data is stored permanently on rom
• not volatile, data not lost when the power goes off
• data in rom cannot be changed

Question 25

RAM - random access memory

Answer 25

- All data in ram is lost when power is switched off (volatile) - data held in ram *CAN* be changed - the processor can write to and read from ram

Question 26

Buses

Answer 26

Multiple lines that connect the cpu and main memory and are used to transfer data and send signals between them

Question 27

Address bus

Answer 27

- uni directional (one way) - specifies the address of the memory location that is to be read from or written to

Question 28

Data bus

Answer 28

Transfers data between main memory and processor. bi-directional (2 way)

Question 29

what can be on the data bus

Answer 29

data an address an instruction

Question 30

Fetch execute cycle

Answer 30

1) Address bus set up with the required address. 2) Read line (on control bus) is activated 3) Instruction is fetched from memory location using the data bus and stored in the instruction register. 4) Instruction in the instruction register is decoded & executed

Question 31

Viruses