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Computer Science: All Topics
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Cambridge IGCSE Computer Science
Computer Science: All TopicsComplete deck
01·1.1 Number systems
What is a bit?
Answer
A binary digit; it can have the value 0 or 1.
02·1.1 Number systems
Why do computers use binary to represent data?
Answer
Digital circuits can reliably distinguish two states, such as on and off.
03·1.1 Number systems
What base does the binary number system use?
Answer
Base 2, using only 0 and 1.
04·1.1 Number systems
What base does the denary number system use?
Answer
Base 10, using digits 0 to 9.
05·1.1 Number systems
What base does hexadecimal use?
Answer
Base 16, using digits 0–9 and letters A–F.
06·1.1 Number systems
What denary values do hexadecimal A, B, C, D, E and F represent?
Answer
A=10, B=11, C=12, D=13, E=14, F=15.
07·1.1 Number systems
What are the place values of an 8-bit unsigned binary number?
Answer
From left to right: 128, 64, 32, 16, 8, 4, 2, 1.
08·1.1 Number systems
What does the least significant bit represent in ordinary binary?
Answer
The rightmost bit, with place value 1 (2⁰).
09·1.1 Number systems
What does the most significant bit mean?
Answer
The leftmost bit, holding the highest place value in the representation.
10·1.1 Number systems
What are the first four hexadecimal place values from right to left?
Answer
1, 16, 256, 4096 (16⁰, 16¹, 16², 16³).
11·1.1 Number systems
How many bits correspond to one hexadecimal digit?
Answer
Four bits.
12·1.1 Number systems
How many different values can 4 bits represent?
Answer
16 values, from 0000 to 1111.
13·1.1 Number systems
What is the largest unsigned denary value in 8 bits?
Answer
255 (11111111₂).
14·1.1 Number systems
What is the smallest unsigned value in an 8-bit binary number?
Answer
0 (00000000₂).
15·1.1 Number systems
How do you convert an unsigned binary number into denary?
Answer
Add the place values of all positions containing a 1.
16·1.1 Number systems
How can you convert a positive denary integer to binary using division?
Answer
Divide repeatedly by 2 and read the remainders from bottom to top.
17·1.1 Number systems
How do you convert binary to hexadecimal?
Answer
Group bits into sets of four from the right; convert each group into a hex digit.
18·1.1 Number systems
How do you convert hexadecimal to binary?
Answer
Replace each hexadecimal digit with its four-bit binary equivalent.
19·1.1 Number systems
How can you convert denary to hexadecimal using division?
Answer
Divide repeatedly by 16 and read the remainders from bottom to top.
20·1.1 Number systems
What is the basic binary addition rule for 1 + 1?
Answer
Write 0 and carry 1 into the next column.
21·1.1 Number systems
What is the binary addition rule for 1 + 1 + 1?
Answer
Write 1 and carry 1 into the next column.
22·1.1 Number systems
What is an overflow error?
Answer
A result is too large to fit within the available number of bits.
23·1.1 Number systems
What is a logical left shift?
Answer
Moving bits to the left and filling vacant right-hand positions with zeros.
24·1.1 Number systems
What is a logical right shift?
Answer
Moving bits to the right and filling vacant left-hand positions with zeros.
25·1.1 Number systems
What does two's complement allow a computer to represent?
Answer
Positive and negative integers using a fixed number of bits.
26·1.1 Number systems
What does a leading 1 indicate in an 8-bit two's complement integer?
Answer
The number is negative.
27·1.1 Number systems
What does a leading 0 indicate in an 8-bit two's complement integer?
Answer
The number is zero or positive.
28·1.1 Number systems
Convert 10110110₂ into denary.
Answer
128 + 32 + 16 + 4 + 2 = 182.
29·1.1 Number systems
Convert 01111001₂ into denary.
Answer
64 + 32 + 16 + 8 + 1 = 121.
30·1.1 Number systems
Convert 142₁₀ into 8-bit binary.
Answer
10001110₂.