OCR A-level Computer Science (H446) - 1.2.4 - Assembly Language

What is assembly language?

• A low-level programming language that uses mnemonic codes to represent machine instructions.

• A language used for creating graphical user interfaces.

• A programming language that is only used for web development.

• A high-level programming language that uses mnemonic codes to represent machine instructions.

Answer explanation

Assembly language is a low-level programming language that uses mnemonic codes to represent machine instructions. It is not used for creating graphical user interfaces or for web development exclusively. Also, it is not a high-level programming language. The mnemonic codes in assembly language correspond directly to the machine language instructions of a specific CPU architecture.

Name one advantage of using assembly language.

• Higher level of abstraction

• Platform independence

• Efficient execution of code

• Easier debugging of code

Answer explanation

The question asks for an advantage of using assembly language. The correct answer is 'Efficient execution of code'. Assembly language is closer to machine code, which allows for more efficient execution of code compared to higher-level languages. Other options like 'Higher level of abstraction', 'Platform independence', and 'Easier debugging of code' are generally not advantages of assembly language.

What are assembly language instructions?

• Low-level instructions executed by a computer's CPU.

• Instructions executed by a computer's RAM.

• Instructions executed by a computer's GPU.

• High-level instructions executed by a computer's CPU.

Answer explanation

Assembly language instructions are low-level instructions that are directly executed by a computer's CPU. They are not executed by the RAM or GPU, nor are they high-level instructions. These instructions are closer to machine code and provide more control over the hardware, which differentiates them from high-level instructions.

How many registers are there in assembly language?

• 1

• 10

• 100

• No fixed number

Answer explanation

The number of registers in assembly language is not fixed. It varies depending on the specific architecture of the computer system. Some systems may have a few registers, while others may have many more. Therefore, the correct answer is 'No fixed number'.

What is the purpose of addressing modes in assembly language?

• To determine the order of execution of instructions.

• To specify the way in which the operands of an instruction are accessed or referenced.

• To define the size of the instruction set.

• To control the flow of program execution.

Answer explanation

The purpose of addressing modes in assembly language is to specify the way in which the operands of an instruction are accessed or referenced. This is not about determining the order of execution, defining the size of the instruction set, or controlling the flow of program execution. It's about how operands are accessed or referenced in an instruction.

What are the different addressing modes in assembly language?

• base mode

• stack mode

• immediate mode, direct mode, indirect mode and indexed mode

• register mode

Answer explanation

The question asks about the different addressing modes in assembly language. The correct answer is 'immediate mode, direct mode, indirect mode and indexed mode'. These are the four primary addressing modes used in assembly language to specify the location of data.

What is the role of registers in assembly language?

• Registers in assembly language are used to store permanent data.

• Registers in assembly language are used to perform arithmetic operations.

• Registers in assembly language are used to store program instructions.

• Registers in assembly language are used to hold temporary data and operands during program execution.

Answer explanation

Registers in assembly language play a crucial role in holding temporary data and operands during program execution. They do not store permanent data, program instructions, or perform arithmetic operations directly. Instead, they serve as temporary storage for data being processed or manipulated within the program.

What is the difference between assembly language and machine language?

• Assembly language is a human-readable low-level programming language that uses mnemonics to represent machine instructions, while machine language is the binary code that the computer's processor can directly execute.

• Assembly language is a high-level programming language, while machine language is a low-level programming language.

• Assembly language is used for web development, while machine language is used for system programming.

• Assembly language is a compiled language, while machine language is an interpreted language.

Answer explanation

The difference between assembly language and machine language lies in their readability and representation. Assembly language is a human-readable low-level programming language using mnemonics to represent machine instructions. In contrast, machine language consists of binary code that the computer's processor can directly execute.

Explain the concept of immediate addressing mode in assembly language.

• Immediate addressing mode is a mode in assembly language where the operand is stored in a separate memory location.

• Immediate addressing mode is a mode in assembly language where the operand is calculated using a specific formula.

• Immediate addressing mode is a mode in assembly language where the operand is directly specified in the instruction itself.

• Immediate addressing mode is a mode in assembly language where the operand is accessed through a register.

Answer explanation

Immediate addressing mode in assembly language refers to the method where the operand is directly specified within the instruction itself. This mode is different from other addressing modes, such as accessing operands through registers or separate memory locations. The correct choice highlights this distinction by stating that the operand is directly specified in the instruction.

How many registers are there in assembly language?

• There are 32 registers in assembly language.

• There are 16 registers in assembly language.

• It depends on the specific architecture.

• There are 8 registers in assembly language.

Answer explanation

The number of registers in assembly language varies depending on the specific architecture. Different processors have different numbers of registers, such as 8, 16, or 32. Therefore, there is no fixed number of registers for all assembly languages.