software notes

What is software?

writing software

• software is written by programmers using programming languages
• programming languages are themselves software
• the CPU can only recognise instructions that are given to it as binary bit patterns
• such instructions are called machine code
• machine code is a low level language which means it works low down at the hardware level
• each machine operation has to be written by the programmer
• writing software in machine code is difficult
• high level languages allow the programmer to set out algorithms without having to worry about every single action carried out by the CPU
• it is difficult to produce robust and reliable software
• writing software is still quite a new activity for humans and there is not a long tradition about how it should be done
• various methods have been invented in order to lay down rules about how writing software should best be approached
• this is the discipline of software engineering

types of software

• system software- software that is written to control and make use of the hardware. acts as an intermediary between the user and the hardware and also between applications and the hardware
• applications are what computer users by computers for. these are programs whcih do the real-world tasks that the users want
• applications need to make use of system software in order to make the hardware do what is required

system software

• consists of operating systems, device drivers, firmware, servers, utilities and interfaces
• often taken to include development tools such as compilers, interpreters, linkers and debuggers

operating systems

• the operating system is a large collection of programs that the hardware what to do
• operating systems are necessary to run all applications, except those which are self booting
• they are found in nearly all computing devices
• oversees such operations as transferring data between memory locations, the CPU and the disks; producing visual displays on the screen; controlling peripherals; protecting data from being accidentally overwritten
• sometimes referred to as a platform
• this means that it provides an environment where applications can run
• applications must be written to conform to a particular platform and this imposes a degree of consistency on them
• applications make use of the kernel to operate the hardware
• ensure that applications are less likely to cause problems with basic memory operations

user interface software

• the user interface is the boundary between the human user and the machine
• lets the user give commands
• asks questions
• displays a response
• operating systems provide different ways of doing these things
• command line interface- requires the user to type commands; these are translated by a command interpreter into signals that the computer can understand; you can completely control a computer system with commands which is why technicians and programmers like using them
• they also find it useful to group commands together in shell scripts to carry out maintenance jobs auomatically
• a shell is software that a user needs to communicate with the kernel

memory management

• operating systems have to decide what goes where in memory
• they have to make…