NEW 1.4.1 Data Types

In floating point representation what is the purpose of the mantissa?

• Stores the actual value

• Tells you if the number is using two's complement or sign and magnitude

• Stores the position of the binary point

• Tells you know if the number is negative or positive

Answer explanation

In floating point binary representation the mantissa is the bits representing the number. The larger the number of bits used for the mantissa the greater the precision of the number that can be stored.

How would you store the base-10 denary number -55 using two's complement in 8-bits?

• 0101 0111

• 0011 0111

• 1100 1001

• 1010 0100

Answer explanation

Two's complement is a method in computing of being able to store positive and negative numbers. The most significant bit (left-most bit) represents the negative value of the place. E.g. If there are 4 bits, each bit place is: -8 4 2 1. If there are 5 bits, each bit place is: -16 8 4 2 1.

What is the hexadecimal number 20 in binary?

• 0000 0010

• 0010 0000

• 0001 0000

• 0001 0100

Answer explanation

To convert a two digit hexadecimal number into binary, take each digit in turn and convert it into a 4 bit nibble. E.g. 20 = 0010 (2) 0000 (0). The number is 0010 0000. Remember in hexadecimal, 10 = A, 11 = B, 12 = C, 13 = D, 14 = E, 15 = F.

What is the number 6 in binary?

• 0000 0110

• 0000 1010

• 0011 1111

• 0000 0111

Answer explanation

The number 6 in binary is represented as 0*8 + 1*4 + 1*2 + 0*1, or 0110.

In this line of code: FOR counter = 1 to 10, what data type should counter be declared as?

• Integer

• String

• Boolean

• Real

Answer explanation

Integers are whole numbers. E.g. 6 is an integer. Integers use less memory than storing numbers with decimal places so a programmer should use an integer if a variable or constant will always be a whole number.

What is the binary number 0011 0100 in hexadecimal?

• 34

• 24

• 38

• 52

Answer explanation

To convert a binary number into hexadecimal, split the number into two nibbles, starting from the right. Change each nibble into the denary equivalent, e.g. 0011 = 3. 0100 = 4. Change each digit into hexadecimal. Remember in hexadecimal, 10 = A, 11 = B, 12 = C, 13 = D, 14 = E, 15 = F.

What is the result of binary left shifting 0100 0010 one digit?

• 0010 0010

• 1000 0100

• 0010 0001

• 0100 0001

Answer explanation

Binary shift operations are used in system programming when doing manipulations to either access registers, or write a particular bit which has a specific use. Using a left shift also has the effect of multiplying a number by multiples of 2.

What is the result of using the XOR mask 1111 0000 with the binary value 1001 1101?

• 0110 1010

• 1001 1101

• 0110 0010

• 0110 1101

Answer explanation

Bitwise masking allows us to isolate and extract, toggle and set bit values in a sequence of bits. Bitwise AND extracts a subset of the bits in the value. Bitwise OR sets a subset of the bits in the value. Bitwise XOR toggles bits.

What does bitwise AND do to a sequence of bits?

• Toggles a subset of the bits

• Extracts a subset of the bits

• Sets a subset of the bits

• None of these

Answer explanation

Bitwise masking allows us to isolate and extract, toggle and set bit values in a sequence of bits. Bitwise AND extracts a subset of the bits in the value. Bitwise OR sets a subset of the bits in the value. Bitwise XOR toggles bits.

What is the result of using an AND mask 0101 1111 with the binary value 0110 0001?

• 0111 1111

• 0100 0001

• 1011 1110

• 1011 1111

Answer explanation

Bitwise masking allows us to isolate and extract, toggle and set bit values in a sequence of bits. Bitwise AND extracts a subset of the bits in the value. Bitwise OR sets a subset of the bits in the value. Bitwise XOR toggles bits.