2. Software, Hardware and the Operating System (OS)

2. Software, Hardware and the Operating System (OS)
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A computer can be logically divided into

hardware - the physical parts of a computer, that you can thump/kick. These include, cpu, ethernet cards, harddisks, memory.
software/program - a set of instructions that tell the hardware what to do. software can be in lots of places
- on media (harddisk, floppy disk, flash stick)
- in the computer's memory (when the software is running)
- built into ROM (read only memory) in hardware.
  software built into hardware that is burned into a ROM and which can't be changed (or changed easily) is callled firmware. e.g. a harddisk uses programs in its ROMs to allow it to read/write to disk.
in many formats
- in text form which needs to be compiled before it runs on the computer
- in binary form which will run directly on a computer.

A particularly important piece of software is the operating system (OS). examples are Linux, MacOS, Windows. The purpose of the OS is to virtualise the hardware.

virtualise: make all hardware appear the same to the user, programs, no matter what piece of hardware is being used underneath.

If you use a harddisk that's IDE, SATA, scsi made by any manufacturer, of any size, the OS will present the harddisk as a storage accessed by the same instructions. The instructions will be different for each OS, but once you've picked your OS, the instructions for accessing the harddisk will be the same no matter what harddisk is in the machine.

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