Into which two broad classes are programming languages divided?

Low-level languages and high-level languages.

Describe machine code.

Machine code is the only language a processor can execute directly. Each instruction is a pattern of binary digits made up of an opcode, which says which operation to perform and in which addressing mode, and one or more operands, which give the value, memory address or register to use. It is specific to one processor family, and writing or reading it by hand is extremely slow and error prone, so it is often written out in hexadecimal for convenience.

Describe assembly language.

Assembly language is a low-level language in which each machine code instruction is written as a short, memorable mnemonic, such as ADD, LDR or B, with its operands written as numbers, labels or register names. It is essentially a human-readable form of machine code, normally with one assembly instruction per machine instruction, and it is translated into machine code by an assembler. Like machine code it is specific to a particular processor's instruction set.

State the main advantage of assembly language over machine code.

It is far easier for a person to write, read and debug, because mnemonics and labels are meaningful where binary patterns are not, and the assembler works out the addresses of labels so the programmer does not have to calculate them by hand. Both give the same control of the hardware, so this readability costs nothing in what the program can do.

AQA A-Level Computer Science 7517

Fundamentals of Programming

Topic overview Data types Programming concepts and program structure Arithmetic operations Relational Operations, Constants and Variables Boolean operations String-handling operations Random numbers and exception handling Subroutines, parameters and return values Variable scope and stack frames Recursive techniques Programming paradigms and the procedural approach Classes, Objects, Inheritance and Polymorphism Aggregation, Composition, Class Diagrams and Design Principles

Fundamentals of Data Structures

Topic overview Data Structures and Abstract Data Types Static and Dynamic Data Structures Queues and Linear Queues Circular and Priority Queues Stacks Graphs Trees Hash tables Dictionaries Vectors and Their Notation Vector Arithmetic and Geometry

Fundamentals of Algorithms

Topic overview Graph traversal Tree traversal Reverse Polish notation Searching algorithms Sorting algorithms Optimisation algorithms

Theory of Computation

Topic overview Logic Problems and Algorithm Constructs Pseudo-Code, Hand-Tracing and Program Correctness Representational Abstraction, Generalisation and Information Hiding Procedural and Functional Abstraction Data Abstraction and Problem Reduction Decomposition and Composition Automation and Finite State Machines Sets and Set Notation Subsets and Set Operations Regular expressions and regular languages Backus-Naur Form and syntax diagrams Comparing Algorithms and Functions Order of complexity and Big-O notation Limits of computation, tractability and heuristics Computable problems and the Halting problem Turing machines

Fundamentals of Data Representation

Topic overview Number systems and the sets of numbers Number bases: decimal, binary and hexadecimal Bits, bytes and units of information Unsigned binary and binary arithmetic Signed binary using two's complement Fixed point and floating point representation Normalisation of floating point numbers Rounding errors, accuracy, range and precision Character coding systems Error checking and correction Bit patterns, analogue and digital Bitmapped graphics Vector graphics Digital representation of sound MIDI and Data Compression Encryption

Fundamentals of Computer Systems

Topic overview Hardware, Software and Its Classification System Software and the Operating System Translators and the Role of the Operating System Classification of programming languages Types of program translator Logic Gates and Their Truth Tables Logic Circuits and D-Type Flip-Flops Half-Adders and Full Adders Boolean algebra

Fundamentals of Computer Organisation and Architecture

Topic overview Internal components, buses and von Neumann and Harvard architectures The Stored Program Concept and the Processor The Fetch-Execute cycle The processor instruction set Addressing modes Machine-Code Operations Shifts, Halting and Assembly Language Programs Interrupts Factors affecting processor performance Input and output devices Secondary storage devices

Fundamentals of Communication and Networking

Topic overview Communication methods Communication basics Network Topology and Types of Networking Wireless networking The Internet and Packet Switching Routing, URLs and Domain Names Firewalls, Worms, Trojans and Viruses Encryption, Digital Signatures and Certificates TCP/IP Standard application layer protocols IP Address Structure and Subnet Masking IP Standards and Public and Private Addresses DHCP and Network Address Translation Client server model Thin- versus thick-client computing

Consequences of Uses of Computing

Topic overview The Four Kinds of Issue in Computing Legislation, Ethical Dilemmas and Case Studies

Systematic Approach to Problem Solving

Topic overview Analysis, Design and Implementation Testing and Evaluation

Fundamentals of Databases

Topic overview Conceptual data models and entity relationship modelling Relational databases Database design and normalisation techniques Structured Query Language (SQL)Client server databases

Big Data

Topic overview Volume, Velocity and Variety Why Big Data Resists Analysis Distributed Processing and Functional Programming Fact-Based Models and Graph Schemas

Fundamentals of Functional Programming

Topic overview Function Types, First-Class Objects and Function Application Partial Function Application and Composition Writing functional programs Lists in functional programming

Fundamentals of Computer Systems

Classification of programming languages

2 things to know
Paper 2

Overview

Recall questions on machine code and assembly language, what makes a language low level, and the advantages and drawbacks of low-level programming.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Evaluation

What are the advantages of low-level programming compared with high-level programming?

Process

Why has high-level programming replaced low-level programming for almost all applications?

Questions from this subtopic

Each one with the model answer underneath.

1
Into which two broad classes are programming languages divided?
Model answer
Low-level languages and high-level languages.
2
Which two languages are considered to be low level?
Model answer
Machine code and assembly language.
3
What makes a language low level?
Model answer
A low-level language is tied to the architecture of a particular processor. Its instructions correspond directly to the operations the hardware provides, it works with registers and memory addresses, and the programmer must express the task as the sequence of individual machine steps that carry it out.
4
Describe machine code.
Model answer
Machine code is the only language a processor can execute directly. Each instruction is a pattern of binary digits made up of an opcode, which says which operation to perform and in which addressing mode, and one or more operands, which give the value, memory address or register to use. It is specific to one processor family, and writing or reading it by hand is extremely slow and error prone, so it is often written out in hexadecimal for convenience.
5
Describe assembly language.
Model answer
Assembly language is a low-level language in which each machine code instruction is written as a short, memorable mnemonic, such as ADD, LDR or B, with its operands written as numbers, labels or register names. It is essentially a human-readable form of machine code, normally with one assembly instruction per machine instruction, and it is translated into machine code by an assembler. Like machine code it is specific to a particular processor's instruction set.
6
State the main advantage of assembly language over machine code.
Model answer
It is far easier for a person to write, read and debug, because mnemonics and labels are meaningful where binary patterns are not, and the assembler works out the addresses of labels so the programmer does not have to calculate them by hand. Both give the same control of the hardware, so this readability costs nothing in what the program can do.

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