Software flashcards

Topic 4: Software

System software vs application software

System software manages the computer and provides a platform for other software (operating system, utilities, device drivers, translators). Application software lets the user do a useful task (word processor, spreadsheet, web browser).

Give five functions of an operating system

Any five of: managing files; handling interrupts; providing a user interface; managing peripherals and drivers; managing memory; managing multitasking; providing a platform for applications; managing security; managing user accounts.

What is an interrupt?

A signal to the processor that something needs attention at once, e.g. a key press, a printer out of paper, a division-by-zero error or a timer. It can come from hardware or software.

What happens when the processor receives an interrupt?

At the end of the current fetch-decode-execute cycle it checks for interrupts. If the interrupt has high enough priority, it saves the current state, runs the interrupt service routine, then restores the state and carries on.

What is a device driver?

A small program that translates operating system commands into signals that a particular peripheral, such as a printer, understands.

High-level vs low-level languages

High-level (e.g. Python): close to human language, easier to write and debug, not tied to one processor. Low-level (machine code, assembly): close to the processor, gives direct control of hardware and memory, but is processor-specific and harder to write.

Compiler vs interpreter

Compiler: translates the whole program before it runs, creating an executable; reports all errors after translation; runs fast without the translator. Interpreter: translates and runs one statement at a time; stops at the first error; needed every run.

What does an assembler do?

It translates assembly language (mnemonics such as LDA and ADD) into machine code.

Name four features of an IDE

Any four of: code editor (with syntax highlighting, auto-completion, auto-correction and pretty printing); error diagnostics; run-time environment; translator; debugging tools such as breakpoints, stepping and variable watching.

How do hardware, firmware and the operating system work together to run an application?

The bootloader (firmware) is run on the hardware at start-up; it loads the operating system, which runs on the firmware; applications are then run on the operating system.

Give the syllabus examples of hardware and software interrupts

Hardware: pressing a key on the keyboard, moving the mouse. Software: division by zero, two processes trying to access the same memory location.