Programmers usually specialize in one or two languages. Applications programmers write software that handles specific jobs. For example, they write programs that used for word processing. They also may work to revise existing software. These programmers often specialize in scientific, engineering, business, or educational applications.
Systems programmers maintain the software that controls the operation of an entire computer system.
This programming also effects communication with peripheral equipment, such as printers. Systems programmers have knowledge of the entire computer system. Therefore, they may help applications programmers find the source of problems in their software programs. Much of the work of computer programmers involves updating, repairing, and modifying code for programs that have already been written. They keep records of their programming steps so that other programmers can work on the software.