1 CS 201 Introduction to C (2) Debzani Deb. 2 Overview C

3 Arithmetic Expressions Operators Data Type of Expression Mixed-Type Assignment Statement Type Conversion through Cast Expressions with Multiple Operators Writing Mathematical Formulas in C
1 CS 201 Introduction to C (2) Debzani Deb
2 Overview C Arithmetic Expressions Formatting Numbers in Program Output Interactive Mode, Batch Mode, and Data Files Common Programming Errors Programming Style
The next slide shows all arithmetic operators. Each operator manipulates two operands, which may be constants, variables, or other arithmetic expressions. Example   sum + (incr* 2)  (B/C) + (A + 0.5).
5 C Operators Arithmetic OperatorMeaningExamples + ( int,double ) Addition is is ( int,double ) Subtraction is is 3.0 * ( int,double ) Multiplication 5 * 2 is * 2.0 is 10.0 / ( int,double ) Division 5 / 2 is / 2.0 is 2.5 % ( int) Remainder5 % 2 is 1
 For example 7.0 / 2.0 is 3.5 but the but 7 / 2 is only 3  The reason for this is that C makes the answer be of the same type as the operands. Remainder: The remainder operator (%) returns the integer remainder of the result of dividing its first operand by its second.  Examples: 7 % 2 = 1, 6 % 3 = 0  The value of m%n must always be less than the divisor n.  / is undefined when the divisor (second operator) is 0..
 Example: What is the type of expression x+y when both x and y are of type int . The data type of an expression depends on the type(s) of its operands.  If both are of type int, then the expression is of type int.  If either one or both is of type double, then the expression is of type double. An expressions that has operands of both int and double is a mixed-type expression..
 Example what is the type of the assignment y = 5/2 when y is of type double . When an assignment statement is executed, the expression is first evaluated; then the result is assigned to the variable to the left side of assignment operator. Warning: assignment of a type double expression to a type int variable causes the fractional part of the expression to be lost.  What is the type of the assignment y = 5.0 / 2.0 when y is of type int .
This is done by placing the desired type in parentheses before the expression. This operation called a type cast.  (double)(5/2) is the double value 2.5, and not 2 as seen earlier.  (int)(3.0/2.0) is the int value 1 When casting from double to int, the decimal portion is just truncated – not rounded..
Unary operators take only one operand  - (negates the value it is applied to) Binary operators take two operands.  +,-,*,/ A single expression could have multiple operators  *
 Nested parenthesized expressions must be evaluated from the inside out, with the innermost expression evaluated first. Rule (b): Operator precedence rule – Multiple operators in the same expression are evaluated in the following order:  First: unary –  Second: *, /, %  Third: binary +,- Rule (c): Associativity rule  Unary operators in the same subexpression and at the same precedence level are evaluated right to left  Binary operators in the same subexpression and at the same precedence level are evaluated left to right..
12 Figure 2.8 Evaluation Tree for area = PI * radius * radius;
13 Figure 2.11 Evaluation Tree and Evaluation for z - (a + b / 2) + w * -y
First, multiplication often can be implied in a formula by writing two letters to be multiplied next to each other. In C, you must state the * operator  For example, 2a should be written as 2 * a. Second, when dealing with division we often have:  This should be coded as (a + b) / (c + d)..
%#d  % - start of placeholder  # - field width (optional) – the number of columns to use to display the output.  d - placeholder for integers int n = 123; printf( %1d\n , n); printf( %3d\n , n); printf( %4d\n , n); 123.
16 Formatting Numbers in Program Output (for double) Use %n.mf for double  % - start of placeholder  n - field width (optional)  m – Number of decimal places (optional)  f - placeholder for real numbers double n = ; printf( %8.0f\n , n); printf( %8.2f\n , n); printf( %8.3f\n , n); printf( %8.4f\n , n); Printf( %.2f\n , n);
17 Interactive Mode, Batch Mode, and Data Files Input Redirection Output Redirection Program-Controlled Input and Output Files
Batch mode - the program scans its data from a data file prepared beforehand instead of interacting with its user..
We assume here that the standard input device is associated with a batch data file instead of with the keyboard. In most system, this association can be accomplished relatively easily through input/output redirection using operating system commands. Instead of calling the program as: $ conversion We would call it as: $ conversion < myinput This redirects the text in the file myinput and uses it as the program input. Here $ represents command prompt..
20 Miles to Kilometers conversion program in interactive mode /* Converts distances from miles to kilometers */ #include /* printf, scanf definitions */ #define KMS_PER_MILE 1.609/* conversion constant */ int main(void) { double miles,//distance in miles kms;//equivalent distance in kilometers //Get the distance in miles printf( Enter the distance in miles> ); scanf( %lf , &miles); //Convert the distance to kilometers kms = KMS_PER_MILE * miles; //Display the distance in kilometers printf( That equals %f kilometers.\n , kms); return (0); }
21 /* Converts distances from miles to kilometers */ #include /* printf, scanf definitions */ #define KMS_PER_MILE 1.609/* conversion constant */ int main(void) { double miles,//distance in miles kms;//equivalent distance in kilometers //Get and echo the distance in miles scanf( %lf , &miles); printf( The distance in miles is %.2f.\n , miles); //Convert the distance to kilometers kms = KMS_PER_MILE * miles; //Display the distance in kilometers printf( That equals %f kilometers.\n , kms); return (0); } Miles to Kilometers conversion program with input redirection.
Prompts In the above program scanf gets a value for miles from the first (and only) line of the data file. Because the program input comes from a data file, there is no need to precede this statement with a prompting message. Instead, we follow the call to scanf with the statement printf( The distance in miles is %.2f.\n ,miles); This statement echo prints or displays the value just stored in miles. Without it, we would have no easy way of knowing what value scanf obtained for miles. Whenever you convert an interactive program to a batch program, make sure you replace each prompt with an echo print after the scanf..
Then you can send the output file to the printer to obtain a hard copy of the program output. The command line: $ conversion > myoutput sends the output of the program conversion to the file myoutput. You can do both input and output redirection by using: $ conversion myoutput.
To do this, you need to: 1.Include stdio.h 2.Declare a variable of type FILE 3.Open the file for reading/writing. 4.Read/write from/to the file. 5.Close the file. In the example (next slide) you will see each of these steps..
25 #include #define KMS_PER_MILE int main(void) { double kms, miles; FILE *inp, *outp; inp = fopen( myinput , r ); outp = fopen( myoutput , w ); fscanf(inp, %lf , &miles); fprintf(outp, The distance in miles is %.2f.\n , miles); kms = KMS_PER_MILES * miles; fprintf(outp, That equals %.2f kilometers.\n , kms); fclose(inp); fclose(outp); return (0); } Miles to Kilometers conversion using program controlled input/output
Run-Time Errors - these are detected and displayed by the computer during the execution of a program. Undetected Errors - many execution errors may not prevent a C program from running to completion, but they may simply lead to incorrect results. Logic Errors - these occur when a program follows a faulty algorithm. Debugging - Finding bugs/errors in the program..
 If a statement has a syntax error, it cannot be translated and your program will not be executed. Common syntax errors:  Missing semicolon  Undeclared variable  Last comment is not closed.
A run-time error occurs when the program directs the computer to perform an illegal operation, such as dividing a number by zero. When a run-time errors occurs, the computer will stop executing your program and will display a diagnostic message  This message may indicate the line where the error was detected..
It is essential that you predict the results your program should produce and verify that the actual output is correct. A very common source of incorrect results in C programs is the input of a mixture of character and numeric data.  These errors can be avoided if the programmer always keeps in mind the scanf’s different treatment of %c and and %d/%1f placeholders. These may also occur if you make a mistake about the evaluation order of an arithmetic expression with multiple operators..
Because logic errors usually do not cause run-time errors and do not display error messages, they are difficult to detect. The only sign of a logic error may be incorrect program output. You can detect logic errors by testing the program thoroughly, comparing its output to calculated results..
 A program that looks good is easier to read and understand than one that is sloppy.  80% of the lifetime cost of a piece of software goes to maintenance.  Hardly any software is maintained for its whole life by the original author.  Program that follow the typical conventions are more readable and allow engineers to understand the code more quickly and thoroughly. Check your text book and some useful links page for some directions..
You should always leave a blank space after a comma and before and after operators such as, −, and =. You should indent the lines of code in the body of a function..
33 White Space Examples int main(void) { int foo,blah; scanf( %d ,foo); blah=foo+1; printf( %d , blah); return 0;} int main(void) { int foo, blah; scanf( %d , foo); blah = foo + 1; printf( %d , blah); return 0; } Bad:Good:
 Format numbers in a way that makes sense for the application.
Indentation does not represent program structure Algorithm is inefficient or difficult to follow Program does not compile Program produces incorrect results. Insufficient testing (e.g. Test case results are different than expected, program branch never executed, borderline case not tested etc.).

1 CS 201 Introduction to C (2) Debzani Deb. 2 Overview C Arithmetic Expressions Formatting Numbers in Program Output Interactive Mode, Batch Mode, and. - ppt download

C Language Elements (II) H&K Chapter 2 Instructor – Gokcen Cilingir Cpt S 121 (June 22, 2011) Washington State University. - ppt download

Introduction & the Basic of C Language

UNR Workplace Based Assessment

PDF) Early prediction of patient discharge disposition in acute

Preface The Bibliography of a Writing Life - by Dylano

C Language Elements (II) H&K Chapter 2 Instructor – Gokcen Cilingir Cpt S 121 (June 22, 2011) Washington State University. - ppt download

Pengantar C/C++. 2 Outline  C overview  C language elements  Variable declarations and data types  Executable statements  General form of a C program. - ppt download

Lecture3. - ppt download

7Ap1ETyQB