# Representation of date

## Representation of date

A remote terminal is connected to a central mainframe computer using the telephone lines.

(a) What device is needed at each end of the telephone line?

(b) What job does this device do?

(c) Here is part of a message that is being sent from the terminal to the central mainframe.

(i) What is a group of 8 bits that represent one of the letters called?

(ii) What is even parity?

(iii) How does the mainframe computer know that the message is wrong?

Write the number 6 in binary.

Using 8-bit two's complement notation, convert the numbers 35 and -35 into binary. Show all your working.

A computer uses 8 bits to represent integers in two's complement form.

(a) Fill in the bit pattern for the highest positive number the computer can hold.

(b) What is the denary value of this number?

What is the decimal equivalent of the hexadecimal number represented by E?

A 5

B 8

C 14

D 15

Graphics symbols on a certain microcomputer are designed on a grid of sixteen squares as shown below.

Each row on the grid is represented by the decimal equivalent of a four bit binary pattern. Each symbol is stored in two bytes of computer memory.

The symbol above is created by the command .

(a) Shade squares on the grid below to show the symbol that would be created by the command .

(b) Write down the command that would produce the graphics symbol shown below.

(c) State the meaning of the following terms:

(i) Bit.

(H) Byte.

Below is a diagram of an output port on a washing machine e.g. when the number 24 (0001 1000) is output the machine is 'told' to spin and to pump.

(a) Describe what happens when:

(i) 7 is output.

(ii) 1 is output.

(iii) 0 is output.