Fig. 1 shows a satellite message divided into bytes. The first byte is a temperature reading and the second byte is a status flag. A ground-station computer...
Question 1 Report
Fig. 1 shows a satellite message divided into bytes. The first byte is a temperature reading and the second byte is a status flag. A ground-station computer uses binary because each bit arrives as one of two radio signal states.
(a) State the total number of bits in the message shown. [1]
(b) Convert the temperature byte to denary. [2]
(c) Give the hexadecimal value of the status byte. [2]
(d) State the number of possible different patterns in the status byte. [1]
(e) Give one reason a computer network may split a message into fixed-size bytes. [2]
Answer Details
Each byte contains 8 bits, so the two displayed bytes make a 16-bit message. A hexadecimal digit represents four bits.
- (a) \(2\times8=\) 16 bits. [1]
- (b) \(00101101_2\) has 1s worth \(32,8,4\), and \(1\):
\[32+8+4+1=45\]45. [2] - (c) Split \(10000001\) into \(1000\;0001\). \(1000=\) 8 [1] and \(0001=\) 1, giving 81. [1]
- (d) An 8-bit status byte has \(2^8=\) 256 possible patterns. [1]
- (e) Fixed-size bytes mean each unit has a known length [1], making storage, transmission, or processing more consistent and easier. [1]
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