General aspects on applications software. Applications software is the program that allow the user to get the required work done. In other words, applications software comprises the .procedures and instructions which enable computer systems to do what the user requires. The software design essentially involves three abstract concepts: algorithms (i.e., procedures, or recipes, for computation - may be numerical or non-numerical, e.g.; sorting, text searching): Data structures which indicate the way in which information is organised in the computer's memory. In other words, the structure indicates whether it is organised in array or tree pattern. File structures represent the way in which large amounts of information is stored on the storage media for example, whether it is organised sequentially, or in direct access, inverted file.
Even though users do not need any in-depth knowledge relating to the above mentioned three concepts, it is desirable to have some understanding of the terminology, since it is commonly used in software suppliers' literature.
Once a software procedure is expressed in such terms, it can be coded into a form which the computer can use, by means of a programming language. There are a number of programming languages in use. It must be emphasised that a computer can only operate on instructions in machine code (binary), and early computers were indeed programmed this way. Assembly language, a more convenient mnemonic form of machine code, is still us id today for specialised applications.