1. Theory Fundamentals
A section of Computer Science, 9608
Listing 10 of 304 questions
A simple program written in assembly language is translated using a two-pass assembler. The table contains some of the tasks performed by a two-pass assembler. Tick (✓) one box in each row to indicate whether the task is performed at the first or second pass. The first row has been completed for you. Task First pass Second pass Creation of symbol table ✓ Expansion of macros Generation of object code Removal of comments The processor’s instruction set can be grouped according to their function. For example, one group is modes of addressing. Identify two other groups of instructions. The table shows assembly language instructions for a processor which has one general purpose register, the Accumulator (ACC), and an Index Register (. Instruction Explanation Op code Operand LDM #n Immediate addressing. Load the denary number n to ACC. LDD Direct addressing. Load the contents of the location at the given address to ACC. LDX Indexed addressing. Form the address from + the contents of the Index Register. Copy the contents of this calculated address to ACC. LDR #n Immediate addressing. Load the denary number n to IX. STO Store contents of ACC at the given address. ADD Add the contents of the given address to ACC. INC Add 1 to the contents of the register (ACC or . CMP #n Compare contents of ACC with denary number n. JPE Following a compare instruction, jump to if the compare was True. JPN Following a compare instruction, jump to if the compare was False. JMP Jump to the given address. OUT Output to screen the character whose ASCII value is stored in ACC. END Return control to the operating system. The current contents of the main memory, Index Register (and selected values from the ASCII character set are: Address Instruction LDM #0 STO 300 CMP #0 JPE 28 LDX 100 ADD 301 OUT JMP 30 LDX 100 OUT LDD 300 INC ACC STO 300 INC IX CMP #2 JPN 22 END … … IX ASCII code table (Selected codes only) ASCII Code Character A B C D E a b c d e
9608_s19_qp_11
THEORY
2019
Paper 1, Variant 1
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The steps 1 to 6 describe the first pass of a two‑pass assembler. The following three statements are used to complete the sequence of steps. A If it is already in the symbol table, it checks to see if the absolute address is known B When it meets a symbolic address, it checks to see if it is already in the symbol table C If it is known, it is entered Write one of the letters A, B or C in the appropriate step to complete the sequence. 1. The assembler reads the assembly language instructions 2. 3. If it is not, it adds it to the symbol table 4. 5. 6. If it is not known, it is marked as unknown. The assembler translates assembly code into machine code. The table shows the denary values for three assembler op codes. Op code Denary value LDD ADD STO Convert the denary value for the op code LDD into 8‑bit binary. Convert the denary value for the op code STO into hexadecimal. State why the denary value for the op code ADD cannot be represented in 8‑bit two’s complement form. Justify your answer. The table shows part of the instruction set for a processor. The processor has one general purpose register, the Accumulator (ACC), and an Index Register (. Instruction Explanation Op code Operand LDM #n Immediate addressing. Load the denary number n to ACC LDD Direct addressing. Load the contents of the location at the given address to ACC LDX Indexed addressing. Form the address from + the contents of the Index Register. Copy the contents of this calculated address to ACC LDR #n Immediate addressing. Load the denary number n to IX STO Store contents of ACC at the given address ADD Add the contents of the given address to ACC INC Add 1 to the contents of the register (ACC or CMP Compare contents of the address given with the contents of ACC JPE Following a compare instruction, jump to if the compare was True JPN Following a compare instruction, jump to if the compare was False JMP Jump to the given address OUT Output to screen the character whose ASCII value is stored in ACC END Return control to the operating system
9608_s20_qp_12
THEORY
2020
Paper 1, Variant 2
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A program is written in assembly language. The op codes LDM and LDD are used to load a register. The op code LDM uses immediate addressing, and the op code LDD uses direct addressing. Describe what happens when the following instructions are run. LDM #300 LDD 300 Assembly language instructions can be grouped by their purpose. The following table shows four assembly language instructions. Tick (✓) one box in each row to indicate the group each instruction belongs to. Instruction Description Jump instruction Arithmetic operation Data movement LDR #3 Load the number 3 to the Index Register ADD #2 Add 2 to the Accumulator JPN 22 Move to the instruction at address 22 DEC ACC Subtract 1 from the Accumulator The processor handles interrupts within the fetch-execute cycle. Give one example of a hardware interrupt and one example of a software interrupt. Hardware Software Explain how the processor handles an interrupt.
9608_s19_qp_13
THEORY
2019
Paper 1, Variant 3
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Assemblers translate from assembly language to machine code. Some assemblers scan the assembly language program twice; these are referred to as two-pass assemblers. The following table shows five activities performed by two-pass assemblers. Write 1 or 2 to indicate whether the activity is carried out during the first pass or during the second pass. Activity First pass or second pass any symbolic address is replaced by an absolute address any directives are acted upon any symbolic address is added to the symbolic address table data items are converted into their binary equivalent forward references are resolved
9608_s15_qp_13
THEORY
2015
Paper 1, Variant 3
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An operating system (OS) is usually pre-installed on a new computer. The OS performs a number of different tasks such as memory management and security management. State three memory management tasks the OS performs. State three security management tasks the OS performs. State two tasks, other than memory management and security management that are carried out by an OS. Utility software is usually pre-installed on a new computer. The following table lists four programs. Put one tick (✓) in each row to indicate whether or not the program is utility software. Program True False Disk Defragmenter Word Processor Library Program Compression Software
9608_s18_qp_11
THEORY
2018
Paper 1, Variant 1
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An operating system (OS) is usually pre-installed on a new computer. The OS performs a number of different tasks such as file management and peripheral management. State three file management tasks the OS performs. State three printer management tasks the OS performs. Utility software is usually pre-installed on a new computer. The following table lists four programs. Put one tick (3) in each row to indicate whether or not the program is utility software. Program True False Database Virus checker Web browser Backup software Name two other utility programs. Program 1 Program 2
9608_s18_qp_12
THEORY
2018
Paper 1, Variant 2
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A computer has an operating system (OS) and utility software. The following table lists key management tasks performed by an operating system and their descriptions. Complete the table by writing the missing management task names and descriptions. Management task Description Memory management Provides user accounts and passwords Handles the signals sent when the attention of the processor is required elsewhere Provision of a software platform A hard disk formatter and a hard disk defragmenter are two examples of utility software. Describe the actions performed by a hard disk formatter and a hard disk defragmenter. Hard disk formatter Hard disk defragmenter Identify three other examples of utility software that can be installed on the computer.
9608_s19_qp_13
THEORY
2019
Paper 1, Variant 3
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Utility programs are examples of system software. Complete the table by writing the name of the utility program for each description. Description Utility program Reorganises files on a disk to improve efficiency Scans a hard disk to identify bad sectors Prepares a hard disk for first use File compression is one example of a utility program. Tick (✓) one box on each row to indicate whether the action is an example of lossy compression or lossless compression. Action Lossy Lossless Reducing the resolution of an image Using run-length encoding on a text file Reducing the sampling rate of a sound file
9608_s20_qp_11
THEORY
2020
Paper 1, Variant 1
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Questions Discovered
304