Computer systems (AS Level) flashcards

Topic 6: Computer systems

Hardware vs software

Hardware is the electronic components of a computer system. Software is the sequences of instructions executed using the hardware.

Name the four types of system software on the 9645 specification

Operating system, utility programs, libraries and translators.

What are libraries?

Collections of pre-written, tested subroutines that programs call, so code is not rewritten and errors are reduced.

Name four functions of an operating system

Scheduling (which process uses the processor next), memory allocation, I/O device management through device drivers, and interrupt handling.

Low-level vs high-level languages: advantages

Low-level: direct control of hardware and registers; can be fast and use little memory. High-level: quicker to write, easier to read, debug and maintain, portable, with libraries available.

What is an imperative high-level language?

A high-level language in which the commands describe the process to be followed to carry out a task.

Compiler vs interpreter

A compiler translates the whole program once, before execution, producing object code that runs fast without the source. An interpreter translates and executes one statement at a time on every run, producing no object code.

How is intermediate (byte) code run?

A virtual machine interprets it, or a just-in-time (JIT) compiler converts it into machine code for the computer it is running on.

Source code vs object code

Source code is the program as written in a high-level or assembly language; it is not directly executable. Object (executable) code is machine code output by a compiler or assembler.