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Introduction to C Programming

CNG 230 Lecture - 1

Programming Languages

• (^) Computer program: data and instructions used to operate a computer and produce a specific result - (^) A program or set of programs is called software.
• (^) Programming: writing instructions in a language that the computer can respond to and that other programmers can understand
• (^) Programming language: set of instructions that can be used to construct a program

Programming languages II

• (^) Assembly language
  • (^) Symbolic notations to machine language are referred to as assembly language.
  • (^) Each class of computer such as IBM PC, Apple and Hewlett-Packard has different machine languages LOAD first ADD second MUL factor STORE answer
  • (^) Programming languages that use this type of symbolic notation are referred as assembly language.

Assemblers

Program translation

How a C program is compiled?

Development of C

• (^) History of C…” Professional Programmer’s Language !”
  • Developed by Denis M. Ritchie at AT&T Bell Labs in 1972 as a systems programming language
  • Used to develop UNIX
  • Used to write modern operating systems
  • Hardware independent (portable)
• Standardization
  • Many slight variations of C existed, and were incompatible
  • Committee formed to create a "unambiguous, machine independent“ definition
  • Standard created in 1989, updated in 1999

Algorithms

• (^) Before a C program is written, a programmer must clearly understand what the data is to be used, the desired result or output , and the steps to be used to produce the result.
• (^) The steps selected to produce the result is referred to as an algorithm.
• (^) “What method will you use to solve the given problem?”

The Power of Algorithms

• (^) Algorithms can be written to solve a multitude of (sometimes very complex) problem
• (^) Yet they are made up of careful combinations of very simple operations
• (^) Simple operations are combined in the following ways
  • (^) sequence - one operation (or group of operations) directly follows another
  • (^) condition (selection) - an operation (or group of operations) is executed, or not executed, based on the results of a yes/no (true/false) decision
  • (^) repetition (loop) - an operation (or group of operations) is executed repeatedly, a given number of times, or until a given condition is true

Algorithms - Pseudocode

• (^) When English phrases are used to describe the algorithm (the processing steps), the description is called pseudocode.
• (^) Example: Set n equal to 100 Set a equal to 1 Set b equal to 100 Calculate sum = n(a+b)/ Display the sum

Case Study: Design and Development

The circumference, C, of a circle is given by the formula C = 2 x PI x r, where PI is the contast 3.14, and r is the radius of the Circle. Using this information, write a C program to calculate the circumference of a circle that has 2-inch radius.

Common Programming Errors

• (^) Rushing to write and execute a program without spending sufficient time on learning about the problem and designing and appropriate algorithm;
• (^) Forgetting to backup a program;
• (^) Not understanding that computers respond only to explicitly defined algorithms.

Summary

• (^) There are low-level (machine, assembly language) and high-level languages (procedural, object-oriented);
• (^) C is a high level language;
• (^) The steps selected to produce the result is referred to as an algorithm.
• (^) Sequence, selection and repetition are key to algorithms;
• (^) Main steps include:
  • (^) Get the inputs to the problem
  • (^) Calculate the desired outputs
  • (^) Report the results of a calculation