Computer programming




Computer programming is the process of writing or editing source code. Editing source code involves testing, analyzing, refining, and sometimes coordinating with other programmers on a jointly developed program. A person who practices this skill is referred to as a computer programmer, software developer, and sometimes coder.

The sometimes lengthy process of computer programming is usually referred to as software development. The term software engineering is becoming popular as the process is seen as an engineering discipline.

Programming languagesedit

Computer programs can be categorized by the programming language paradigm used to produce them. Two of the main paradigms are imperative and declarative.

Imperative languagesedit

Imperative programming languages specify a sequential algorithm using declarations, expressions, and statements:

  • A declaration couples a variable name to a datatype – for example: var x: integer;
  • An expression yields a value – for example: 2 + 2 yields 4
  • A statement might assign an expression to a variable or use the value of a variable to alter the program's control flow – for example: x := 2 + 2; if x = 4 then do_something();

One criticism of imperative languages is the side effect of an assignment statement on a class of variables called non-local variables.

Declarative languagesedit

Declarative programming languages describe what computation should be performed and not how to compute it. Declarative programs omit the control flow and are considered sets of instructions. Two broad categories of declarative languages are functional languages and logical languages. The principle behind functional languages (like Haskell) is to not allow side effects, which makes it easier to reason about programs like mathematical functions. The principle behind logical languages (like Prolog) is to define the problem to be solved – the goal – and leave the detailed solution to the Prolog system itself. The goal is defined by providing a list of subgoals. Then each subgoal is defined by further providing a list of its subgoals, etc. If a path of subgoals fails to find a solution, then that subgoal is backtracked and another path is systematically attempted.

Compilation and interpretationedit

A computer program in the form of a human-readable, computer programming language is called source code. Source code may be converted into an executable image by a compiler or assembler, or executed immediately with the aid of an interpreter.

Compilers are used to translate source code from a programming language into either object code or machine code. Object code needs further processing to become machine code, and machine code consists of the central processing unit's native instructions, ready for execution. Compiled computer programs are commonly referred to as executables, binary images, or simply as binaries – a reference to the binary file format used to store the executable code.

Some compiled and assembled object programs need to be combined as modules with a linker utility in order to produce an executable program.

Interpreters are used to execute source code from a programming language line-by-line. The interpreter decodes each statement and performs its behavior. One advantage of interpreters is that they can easily be extended to an interactive session. The programmer is presented with a prompt, and individual lines of code are typed in and performed immediately.

The main disadvantage of interpreters is computer programs run slower than when compiled. Interpreting code is slower because the interpreter must decode each statement and then perform it. However, software development may be faster using an interpreter because testing is immediate when the compiling step is omitted. Another disadvantage of interpreters is an interpreter must be present on the executing computer. By contrast, compiled computer programs need no compiler present during execution.

Just in time compilers pre-compile computer programs just before execution. For example, the Java virtual machine Hotspot contains a Just In Time Compiler which selectively compiles Java bytecode into machine code – but only code which Hotspot predicts is likely to be used many times.

Either compiled or interpreted programs might be executed in a batch process without human interaction.

Scripting languages are often used to create batch processes. One common scripting language is Unix shell, and its executing environment is called the command-line interface.

No properties of a programming language require it to be exclusively compiled or exclusively interpreted. The categorization usually reflects the most popular method of language execution. For example, Java is thought of as an interpreted language and C a compiled language, despite the existence of Java compilers and C interpreters.

Comments

Post a Comment

Popular posts from this blog

49)Discussed: What to expect on Republic Time 2021and what not to

India Republic Day -- Republic Day 2021: In 2020it was the agitation against the Citizenship Amendment Act (CAA). Nowthousands of farmersgenerally from Punjab and Haryanahave been camping at the borders of Delhi for more than 2 monthsdemanding the Centre repeal the three farm laws. For that second year in a lineRepublic Day celebrations from the national capital will be presented under the shadow of strong protests against laws approved by the Centre. In 2020it was the agitation against the Citizenship Amendment Act (CAA). This timethousands of farmersgenerally from Punjab and Haryanahave been camping at the borders of Delhi for more than 2 monthsdemanding the Centre repeal the three farm laws. This kind of years Republic Day attend will also be the first major open event in pandemic times. What is new this year The case will be pared down in terms of the number of spectatorsthe size of walking in line contingents and other side destinations. The spectator size have been reduced to
Read more

Storage and execution

Image
Typically, computer programs are stored in non-volatile memory until requested either directly or indirectly to be executed by the computer user. Upon such a request, the program is loaded into random-access memory, by a computer program called an operating system, where it can be accessed directly by the central processor. The central processor then executes ("runs") the program, instruction by instruction, until termination. A program in execution is called a process. Termination is either by normal self-termination, by user intervention, or by error – software or hardware error. Simultaneous execution edit Many operating systems support multitasking which enables many computer programs to appear to run simultaneously on one computer. Operating systems may run multiple programs through process scheduling – a software mechanism to switch the CPU among processes often so users can interact with each program while it runs. Within hardware, modern day multiprocessor computers
Read more

History

Image
Code-breaking algorithms have existed for centuries. In the 9th century, the Arab mathematician Al-Kindi described a cryptographic algorithm for deciphering encrypted code, in A Manuscript On Deciphering Cryptographic Messages . He gave the first description of cryptanalysis by frequency analysis, the earliest code-breaking algorithm. Early programmable machines edit The earliest programmable machines preceded the invention of the digital computer. As early as the 9th century, a programmable music sequencer was invented by the Persian Banu Musa brothers, who described an automated mechanical flute player in the Book of Ingenious Devices . In 1206, the Arab engineer Al-Jazari invented a programmable drum machine where musical mechanical automata could be made to play different rhythms and drum patterns. In 1801, Joseph-Marie Jacquard devised a loom that would weave a pattern by following a series of perforated cards. Patterns could be woven and repeated by arranging the cards. Analytica
Read more