The instructions for a computer program are sometimes referred to as . computer programmers focus on computer programs, but they also plan, test, and document computer programs. in contrast,software apply formalized techniques to reduce the cost and complexity of software while increasing reliability. before program code can be written, a programmer needs a clear problem , which includes a list of assumptions, a description of known information, and a specification for what constitutes a solution. programming projects can be approached using a(n) methodology, which requires extensive planning and documentation up front. an alternative approach is to use the methodology in which programs are developed in iterations called . with a clear plan, a programmer can begin coding using a text editor, program editor, or development environment. programs are composed of a series of statements that include a(n) such as input or print and parameters. those parameters may include that represent values that can change, or that represent unchanging values. all computer programs should include internal documentation in the form of , which are explanatory comments inserted into a computer program along with lines of code. a program is not complete until it has been tested to ensure that it contains no errors, logic errors, or runtime errors. programmers can use methods based on rigorous logical and mathematical models to reduce the number of defects in a software product. additional techniques for producing high-quality, secure code include threat modeling and programming.