← IGCSE Computer Science Paper 1

Low-level language

A programming language close to the CPU's instructions, such as machine code or assembly language. Each instruction is one simple CPU operation, so it is harder for people to read.

Part of: IGCSE Computer Science 0478 — 4.2 Programming Languages, Translators and IDEs — Module 4

Understanding Low-level language in IGCSE Computer Science Paper 1

What it does: An assembly instruction like ADD R1, R2 does one small CPU operation, unlike a high-level line that may do many. Low-level languages are close to the hardware. High-level languages are closer to English. Machine code is made of binary instructions for the CPU, so it is the lowest level of language.

Common mistakes: The assembly mnemonic for adding is ADD, not AAD. Each mnemonic stands for exactly one simple CPU operation, so it must be spelled correctly. The line should be ADD 11. In this assembly language the mnemonic that loads a value into the accumulator is LDA. LOAD is not a valid instruction. The line should be LDA 20.

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This module's key terms are also in a printable crossword (Modules 419–429) and word search (Modules 419–439).

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Learning

Duo

Which of these is a low-level language?

Assembly languagePython

Matches

Assembly language is a high-level language because it uses words

↓

Assembly language is low-level, not high-level. Its mnemonics map closely to CPU instructions.

Applying

Meanings

Term

low-level language

Meaning

A programming language close to the CPU's instructions, such as machine code or assembly language. Each instruction is one simple CPU operation, so it is harder for people to read.

Practice

LDA 20

Testing

Gaps

10 ; load 10 into the accumulator

Check Answer

Spots

1LDA 10

2AAD 11

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Quick Questions

1. Which of these is a low-level language?

A. Assembly language ✓

B. Python

Assembly language and machine code are the two kinds of low-level language. Python is a high-level language.

2. A low-level language is close to...

A. everyday English

B. the instructions the CPU understands ✓

Low-level languages are close to the hardware. High-level languages are closer to English.

3. In a low-level language, each instruction usually does...

A. one simple CPU operation ✓

B. many complex tasks at once

Each low-level instruction is one simple CPU operation, such as loading a value or adding two numbers.

4. Which statement is true?

A. Machine code is a high-level language

B. Machine code is a low-level language ✓

Machine code is made of binary instructions for the CPU, so it is the lowest level of language.

5. Why are low-level programs harder for people to read?

A. They use simple CPU-level instructions instead of English-like commands ✓

B. They are always written in a different alphabet

Low-level code is close to the hardware, so it is harder to read than high-level code. It does not use another alphabet.

Match the Pairs

LDA 5 → An assembly language instruction that loads a value into the CPU, so it is a low-level language

10110000 01100001 → Machine code, the binary instructions the CPU understands directly

Each low-level instruction is one simple CPU operation, such as adding two values → ADD R1, R2

Low-level code is close to the hardware, so one high-level line becomes many instructions → total = a + b -> LDA a / ADD b / STA total

Assembly language is a high-level language because it uses words → Assembly language is low-level, not high-level. Its mnemonics map closely to CPU instructions.

Low-level languages are easy for people to read because they are close to English → Low-level languages are close to the hardware, not to English, so they are harder for people to read.

Key Term

low-level language

A programming language close to the CPU's instructions, such as machine code or assembly language. Each instruction is one simple CPU operation, so it is harder for people to read.

Fill in the Blanks

1. LDA 10 ; load 10 into the accumulator

Hint: Type the assembly mnemonic that loads a value into the accumulator.

2. LDA 10 ADD 5 ; add 5 to the accumulator

Hint: Type the mnemonic for adding a value to the accumulator.

3. LDA 10 ADD 5 STO total ; store the result

Hint: Type the mnemonic that stores the accumulator into memory.

4. LDA 20 ; load twenty into the accumulator

Hint: Type the number the comment says should be loaded.

5. STO total END ; stop the program

Hint: Type the mnemonic that ends the program.

Spot the Error

Question 1

A LDA 10

B AAD 11

C STO 12

D END

Line B — The assembly mnemonic for adding is ADD, not AAD. Each mnemonic stands for exactly one simple CPU operation, so it must be spelled correctly. The line should be ADD 11.

Question 2

A LOAD 20

B SUB 21

C STO 22

D END

Line A — In this assembly language the mnemonic that loads a value into the accumulator is LDA. LOAD is not a valid instruction. The line should be LDA 20.

Question 3

A LDA 5

B ADD 6

C STO 7,8

D END

Line C — A low-level instruction does one simple operation, so STO takes a single address. It cannot store to two places at once. The line should be STO 7.

Question 4

A 00000001 00002010

B 00000010 00001011

C 00000011 00001100

Line A — Machine code is written only in binary, using 0s and 1s. The digit 2 is not allowed. The line should be 00000001 00001010.

Question 5

A 00000001 00000101

B 00000010 00000110

C 0000011 00000111

D 11111111

Line C — Every machine code instruction here has an 8-bit opcode. This one is missing a bit, so the CPU would read it wrongly. The line should be 00000011 00000111.

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