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Variables and Declarations

Learn how to create and use variables with correct identifiers in your C programs. Understand the rules for naming variables, declare variables with their types, and initialize them for effective programming. Practice with examples and assignments to enhance your skills in variable usage.

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Variables and Declarations

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  1. Variables and Declarations 02/06/15

  2. Objectives • Create and use variables in a program. • Use correct identifiers for the variables' names.

  3. Identifiers • Names of things • Way to name a variable • Rules • Begin with letter or underscore • Contain letters, underscores and digits • Cannot be a keyword • Examples: num1 Ghost51 mill_house _river_flow TAX

  4. Keywords • Words with special meaning in C • Cannot be used as variable names • float, return • See p.44, Table 2.1

  5. Invalid Identifiers • Why are these invalid? 12noon potato# green-tea double

  6. Variables • Place to store a value in memory • Declare: float cost; • Change Contents cost = 15.00; cost = 10.00; • Can only store one number at a time.

  7. Variable Declarations • Variable type • Followed by identifier that is the variable's name. int counter; float x; char answer;

  8. Example Program with Variables • lincoln.c

  9. Initialization • Give variable initial value • Don't know what is stored there otherwise. • lbsFood.c • Count is initialized to 3.

  10. Write a Program • Look at exercise #4, p. 89 The distance that light travels in one year is called a light year. Given that light travels at a speed of 3 X 108 meters in one second, determine the distance of a light year. The distance formula is d = rt. Output the answer in kilometers. I will submit the program.

  11. Assignments • On your own: • p. 52 #1, p. 65 #1,4, p. 72 #1, #2a,c,d,f,e, #3a,c,d,f,h, p.84 #4 a,b, #7, p. 113#1a,c, 2 a,c,e,g, p.128 #2 a,b,c • Put programs for the problems in a directory and submit them together as program 3: • P. 89 #6

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