Computer programming

Computer programming Quick review…..

Types of programming languages Machine language Only language computer directly understands “Natural language” of computer Defined by hardware design Machine-dependent Generally consist of strings of numbers Ultimately 0s and 1s Instruct computers to perform elementary operations One at a time Cumbersome for humans Example: +1300042774 +1400593419 +1200274027

Types of programming languages Assembly language English-like abbreviations representing elementary computer operations Clearer to humans Incomprehensible to computers Translator programs (assemblers) Convert to machine language Example: LOAD BASEPAY ADD OVERPAY STORE GROSSPAY

Types of programming languages High-level languages Similar to everyday English, use common mathematical notations Single statements accomplish substantial tasks Assembly language requires many instructions to accomplish simple tasks Translator programs (compilers) Convert to machine language Interpreter programs Directly execute high-level language programs Example: grossPay = basePay + overTimePay

What are Interpreters, compilers and assemblers? it converts each high level instruction into a series of machine instructions and then immediately run (or execute) those instructions. Compilers: convert a finished program (or section of a program) into object code. This is often done in steps. Assemblers: program which convert the symbolic instructions ( which is written in an assembly language) into object or machine code.

size of programs Programs are generally divided into three basic sizes: trivial, small, and large. Trivial programs are programs that a skilled programmer can write in less than two days of coding. Small programs are programs that one skilled programmer can write in less than one year of full time work.

Con. Size of programs Large programs are programs that require more than two to five man-years of labour, normally written by programming teams (which can exceed 1,000 skilled workers).

Nice stories Larry Ellison wrote the first version of Oracle database by himself in about six months. That is a genius exception. Data bases typically take large teams (sometimes hundreds of programmers) at least a year. Another story Bill Gates, copying and pasting from the source code of three working open source versions, took more than six months to create a bug-filled BASIC compiler and then hired a team of six skilled programmers who spent more than six more months to get rid of enough bugs to make the compiler somewhat usable (a total of more than three man-years).

That is an exception. A BASIC compiler typically takes a skilled programmer a few hours to create. Note that Bill Gates takes credit for quickly having created a BASIC compiler, but according to other sources he was sued for having illegally used open source code for commercial purposes, forcing him to spend a great deal of time attempting to do a project that many programmers of the day could successfully finish in hours.

History of programming languages There have been thousands of programming languages, many of which have been lost to history. FORTRAN (FORmula TRANslation) was created in 1954 by John Backus and other researchers at International Business Machines (now IBM). Released in 1957. FORTRAN is the oldest programming language still in common use. FORTRAN was the first high-level language, using the first compiler ever developed.

Cont. History Prior to Fortran, programmers were required to program using machine / assembly languages. Significant features of the language are listed below:” Simple to learn. Machine Independent ( easy transportation). Efficient execution. Ability to control storage allocation (considered today as a dangerous practice)

Cont. History LISP LISP (LISt Processing) was created n 1958. released in 1960 by John McCarthy of MIT. the second oldest programming language still in common use. was intended for writing artificial intelligence programs.

Cont. History COBOL COBOL (COmmon Business Oriented Language) was created in May 1959 by the Short Range Committee of the U.S. Department of Defense (DoD). Numbers of versions. The last one in 2002. 1997 and 2002 were Object Oriented versions.

Cont. History BASIC BASIC (Beginner’s All-purpose Symbolic Instruction Code) was designed as a teaching language in1963 by John George and Thomas Eugene Kurtz of Dartmouth College. BASIC was intended to make it easy to learn programming. The first BASIC program was run at 4 a.m. May 1, 1964.

Cont. History Pascal Pascal (named for French religious fanatic and mathematician Blaise Pascal) was created in 1970 by Niklaus Wirth. Work started in 1968. Pascla intended as a teaching language to replace BASIC.

Cont. History C C was developed from 1969-1972 by Dennis Ritchie. Was developed for use in systems programming for UNIX. SQL SQL (Standard Query Language) was designed by Donald D. Chamberlin and Raymond F. Designed by IBM in 1974.

Cont. History Ada Ada was first released in 1983 (ADA 83), other releases in 1995 (ADA 95) and 2005 (ADA 2005). Ada was created by the U.S. Department of Defence (DoD). originally intended for embedded systems and later intended for all military computing purposes. C++ c++ was developed in 1983 by Bjarne Stroustrup at Bell Telephone Laboratories. to extend C for object oriented programming.

Cont. History Java Java (named for coffee). was created by James Gosling and others at Sun Microsystems for embedded systems. released for applets in 1995. Original work started in 1991 as an interactive language under the name Oak. Rewritten for the internet in 1994.

Cont. History JavaScript JavaScript (originally called LiveScript). was created by Brendan Elch at Netscape in 1995. A scripting language for web pages. PHP PHP (PHP Hypertext Processor) was created by Rasmus Lerdorf in 1995. C# C# was created by Anders Hajlsberg. The main language of Microsoft’s .NET.