chapter 2 overview of c instructor: kun-mao chao ( 台大資工 趙坤茂 )

Chapter 2Overview of C

Instructor: Kun-Mao Chao(台大資工 趙坤茂 )

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C Language Elements in Miles-to-Kilometers Conversion Program

保留字 . See Appendix E. (p. 819)宣告 (declaration). See. Sec. 2.2.

See Appendix B. (p. 789)

Operator (運算子 ) See Appendix C. (p. 807)

p. 36

Identifier, pp. 38

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Memory Before and After Execution of a Program

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Before and After assignment of a variable

kms = KMS_PER_MILE * miles;

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Before and After Assignment of a Variable

sum = sum + item;

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How to Read Input from the End User

scanf("%lf", &miles);

“%lf” stands for reading a double variable.

“&miles” is the memory address where the double variable will be stored.

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How to Read Input from the End User

scanf("%c%c%c", &first, &middle, &last);

“%c” stands for reading a character variable.

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General Form of a C Program

preprocessor directives: #include and #define

Any used variable in the program should be declared before the usage.

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The Execution for Multiple Operators (1/2)

The execution of multiple operators can be expressed as an evaluation tree.

First, evaluate c=PI* radius

Then, evaluate area=c* radius

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The Execution for Multiple Operators (2/2)

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Evaluation Tree and Evaluation for v = (p2 - p1) / (t2 - t1)

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Evaluation Tree and Evaluation for z - (a + b / 2) + w * -y

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Homework #1

• Write a program to convert a temperature in degrees Fahrenheit to degrees Celsius– Formula: celsius = 5/9 * (fahrenheit - 32)– Hint: revise the Miles-to-Kilometers conversion

program.

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Outline of Lab. This Week

• How to create an empty project– TA is sorry for the mistake last week due to the

non-empty project.

• How to write a program efficiently– Introduction to the debugging skill and tool

• Please refer to Appendix G (p. 829) for Visual C++ IDE (Integrated Development Environment).

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Case Study: Finding the Value of Coins (1/3)

• Write a program to determine the value of a collection of coins– e.g., quarters, dimes, nickels, and pennies.

• The algorithmic flow:– 1. Get and display the customer’s initials.– 2. Get the count of each kind of coin.– 3. Compute the total value in cents.– 4. Find and display the value in dollars and

change.

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Case Study: Finding the Value of Coins (2/3)

1. Read the initials of the customer

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Case Study: Finding the Value of Coins (3/3)

2. Read the count of each kind of coins

3. Compute the total value in cents

4. Find and display the value in dollars and change

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The input can be read from a file instead of from the user.

The output can be written into a file instead of on the screen.

Read input from a file

Write the result into a file

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A Program with Syntax Errors

Syntax error occurs when the code violates grammar rules of C and is detected by the compiler.

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A Program with a Run-Time Error

Run-time error occurs when the program directs the computer to perform an illegal operation (e.g., divide by zero).

temp=0divide by zero

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A Common Error with Carriage Return

Read “2003”

Read “\n”, “B”, “M” instead of “B”, “M”, “C”

Suppose the user input “2003” and press enter key.Then input “BMC” and press enter key.

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A Common Error That Produces Incorrect Results Due to & Omission

scanf does not know where to store the value entered by the user, and just use the original value stored in first and second.

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Outline of Lab. Lecture This Week

• Demo of your Homework #1.– Please bring the source code and executable

file.

• Your homepage

• Other Visual C++ 6.0 editing functionalities.

• File management in Visual C++ 6.0.