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1.1. Data Representation
A subsection of Computer Science, 9618, through 1. Information representation
Listing 10 of 10 questions
A computer uses the ASCII character set. State the number of characters that can be represented by the ASCII character set and the extended ASCII character set. ASCII Extended ASCII Explain how a word such as ‘HOUSE’ is represented by the ASCII character set. Unicode is a different character set. The Unicode value for the character ‘1’ is denary value 49. Write the hexadecimal value for the Unicode character ‘1’. Write the denary value for the Unicode character ‘5’.
9618_s21_qp_12
THEORY
2021
Paper 1, Variant 2
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Text and numbers are examples of data stored in a computer. A character set is used to represent characters in a computer. Describe what is meant by a character set. Identify two character sets and state one difference between them. Character set 1 Character set 2 Difference Describe how lossless compression can be used to reduce the file size of a text file. Explain why lossy compression should not be used on a text file. A computer can represent numerical data in different forms. Complete the table by writing the answer to each statement. Statement Answer The hexadecimal value 11 represented in denary The smallest denary number that can be represented by an unsigned 8-bit binary integer The denary number 87 represented in Binary Coded Decimal (BCD) The denary number 240 represented in hexadecimal The denary number –20 represented in 8-bit two’s complement binary Working space
9618_s22_qp_13
THEORY
2022
Paper 1, Variant 3
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The table shows part of the instruction set for a processor. The processor has one general purpose register, the Accumulator (ACC). Instruction Explanation Opcode Operand AND #n Bitwise AND operation of the contents of ACC with the operand AND Bitwise AND operation of the contents of ACC with the contents of XOR #n Bitwise XOR operation of the contents of ACC with the operand XOR Bitwise XOR operation of the contents of ACC with the contents of OR #n Bitwise OR operation of the contents of ACC with the operand OR Bitwise OR operation of the contents of ACC with the contents of can be an absolute or a symbolic address # denotes a denary number, e.g. #123 The ACC currently contains the following positive binary integer: Write the bit manipulation instruction that would change the binary integer in ACC to: Opcode Operand The ACC currently contains the following positive binary integer: Write the bit manipulation instruction that would change the binary integer in ACC to: Opcode Operand Convert the following positive binary integer into hexadecimal. 0 1 1 1 1 1 1 0 A three-place logical shift to the left is performed on the following positive binary integer. Show the result of this logical shift. 0 1 1 1 1 1 1 0 Convert the denary numbers 127 and 12 to 8-bit binary and then perform the subtraction 12 − 127 in binary. Show your working. 127 in binary 12 in binary 12 − 127 in binary
9618_s22_qp_12
THEORY
2022
Paper 1, Variant 2
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A register stores the following binary number: The binary value in the register represents an unsigned binary integer. Convert the unsigned binary integer into denary. The binary value in the register represents a two’s complement binary integer. Convert the two’s complement binary integer into denary. The binary value in the register represents a hexadecimal number. Convert the binary number into hexadecimal. State why the value in the register cannot be interpreted as a Binary Coded Decimal (BCD). The binary contents of two registers are: Register 1 Register 2 Add the contents of Register 1 and Register 2. Show your working. Answer Subtract the contents of Register 2 from the contents of Register 1. Show your working. Answer
9618_w21_qp_12
THEORY
2021
Paper 1, Variant 2
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Questions Discovered
10