Chapter 13 Programming and Languages

Chapter 13 - Programming and Languages Programming is a problem solving procedure. Program: is a list of instruction for the computer to follow to accomplish the task of processing data into information. The instruction made up of statements used in a programming language such as c++, java, visual basic. Programs can be created or custom-made. Programming also known as software development, follows six-step process known as the software development life cycle (SDLC): 1- Program specification. 2- Program design. 3- Program code. 4- Program test. 5- Program documentation. 6- Program maintenance. -Computer professionals known as software engineering or programmers, use this six-step procedure. -software engineers were ranked near the top of over 100 widely help job based on salary, prestige, and security. Step 1 : program specification Also called program definition or program analysis. It's require the programmer to specify five items: 1) Program objectives 2) Desired output: it's best to specify output before input you need to list what you want to get out of the computer system. Then you determine what will go into it . - the best way to do this is to draw a picture, you – the end user not the programmer- should sketch or write how you want the output to look when it's done. 3) Input data 4) Processing requirements: here you define the processing tasks that must happen for input data to be processed into output. 5) Program specification document : you should record program objectives, desired output, needed input, and required processing, this leads to program design. 59 Step 2 : Program design Here you plan a solution, preferably using structured programming techniques, these techniques consist of : 1) top-down program design: use it to identify the program's processing steps, such steps are called program modules, each module is made up of logically related program statements. Under the rules of top down design, each module should have a single function, the program must pass in sequence from one module to the next until all modules have been processed by the computer. 2) Pseudocode: outline of the logic of the program you will write (like doing a summary of the program before it is written). 3) Flowcharts: here we are concerned with program flowcharts. These graphically present the detailed sequence of steps needed to solve a programming problem. *One of the most powerful capabilities of computers is their ability to make logical comparisons. 4) Logic structures: the best way to link various parts of flowchart is a combination of three logic structures called sequential, selection, repetition. * Sequential: one program statement follows another; there is no question of "yes" or "no" or decision suggesting other consequences. * Selection: occurs when a decision must be made. The outcome of the decision determines which of two paths to follow. Also known as (IF-THEN-ELSE structure ) because that is how you can formulate the decision. * Repetition or loop: describes a process that may be repeated as long as a certain condition remains true. It's called "loop" or "iteration" because the program loops around again and again. **You have to document the logic of the design. ** Step 3 : program code Writing the program called coding. Here you use the logic you developed in the design step to actually write the program. And it's instructs the computer what to do. The good program: the qualities of good program : -Reliable: it should work under most conditions and produce correct output . – it should catch obvious and common input errors. - It should be well documented and understandable by programmers other than the person who wrote it. *One of the best ways to cod effective program is to write so-called structured program. 60 Coding : Programming language uses a collection of symbols, words, and phrases that instruct a computer to perform specific operations. Programming languages process data and information for a wide variety of different types of applications. After coding the program, the next step is testing or debugging it. Step 4 : program test Debugging refers to the process of testing and then eliminating errors, it means sunning the program on a computer and then fixing the parts that do not work. Two types of errors : 1- Syntax errors: violation of the rules of the programming language. (e.x: the (;) in c++ ) 2- Logic errors: occurs when the programmer uses an incorrect calculation or leaves out a programming procedure. testing process: methods devised for finding and removing errors : - Desk checking: (code review) a programmer sitting at a desk checks (proofreads) a printout of the program; the programmer goes through the listing line by line carefully looking for syntax errors and logic errors. - Manually testing with sample data: using a calculator and sample data, a programmer follows each program statement and preforms every calculation, looking for logic errors. The programmer compares the manually calculated values to those calculated by the programs. - Attempt at translation: a program is run through a computer, using a translator program. The translator attempts to translate the written program form the programming language into the machine language. Before the errors will be identified by the translating program. - Testing sample data on the computer: after all syntax errors have been corrected, the program is tested for logic errors. Sample data is used to test the correct execution of each program statement. - Testing by a select group of potential users: (beta testing), the final step in testing a program. Potential users try out the program and provide feedback. 61 Step 5 : program documentation Documentation consists of written descriptions and procedures about a program and how to use it. It's carried on throughout all the programming steps. In this step all the prior documentation is reviewed, finalized, and distributed. It's important for : 1- users : They need to know how to use the software. And they learn it by training courses or by written documentation like printed manuals and the help option within most apps . 2- Operators : documentation must be provided for computer operators. If the program sent them errors messages, they need to know what to do about them. 3- programmers : This kind of documentation should include text and program flowcharts, program listing, and sample output, and might include system flowcharts to show how the particular program relates to other programs within an information system. Step 6 : program maintenance : An important activity, that special job title "Maintenance programmer", and 75% of the total lifetime cost for an application program is for maintenance. The purpose of maintenance is to ensure that current programs are operating error-free, efficiently and effectively. Activities in this area : 1) operations : concern locating and correcting operational errors, making programs easier to use, and standardizing software using structured programming techniques. These activities should be minimal for properly designed programs. - Programming modifications or corrections are often referred to as patches. If the patches are significant, they are known as software updates. 2) changing needs : programs need to be adjusted for a variety of reasons,(including : new tax laws, new information needs, and new company policies). A software project sequentially follows the six steps of software development. However, some project starts before all requirements are known. In these cases, the SDLC becomes a more cyclical process, repeated several times throughout the development of the software. 62 CASE and OOP There is two resources that promised to help in efficiency and productively : CASE tools : (computer-aided software engineering ) provided some automation and assistance in program design, coding , and testing. Object-Oriented software development : focuses less on the procedures and more on defining the relationships between previously defined procedures or "objects" OOP : is a process by which a program is organized into objects. Each object contains both the data and the processing operations necessary to perform a task . 63