1. TDBA66, VT-03 Lecture - Ch. 21 A complete C-program Display Fig. 2.1 and comment on different things such as Preprocessor directives Header files Identifiers Directives Constants Variables Standard Identifiers (Predefined functions)1 Punctuations Special symbols Reserved words

2. TDBA66, VT-03 Lecture - Ch. 22 Figure 1.11 Miles-to-Kilometers Conversion Program /* * Converts distance in miles to kilometers. */ #include /* printf, scanf definitions */ #define KMS_PER_MILE 1.609 /* conversion constant */ int main(void) { double miles, /* input - distance in miles. */ kms; /* output - 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); } Sample Run Enter the distance in miles> 10.00 That equals 16.090000 kilometers.

3. TDBA66, VT-03 Lecture - Ch. 23 User defined identifiers Consists of letters, digits, underscore Cannot begin with a digit A C-reserved word cannot be used A standard identifier should not be redefined Don’t use more than 31 charcters Examples: Letter, letter_1, myfunc_1, square_meter

4. TDBA66, VT-03 Lecture - Ch. 24 Variables and data types Variables are names of different memory cells that can hold values of different types The name of a variable is an identifier A variable should be declared as a certain data type Examples: int n, no_of_students; float score, sum, mean_value;

5. TDBA66, VT-03 Lecture - Ch. 25 Example cont. double miles; /* miles from here to there*/ char letter, digit; Variables of type int can store integers in [INT_MIN, INT_MAX] and similar for float and double but they can store a real number with an integral and fractional part A char can hold one single charcter

6. TDBA66, VT-03 Lecture - Ch. 26 How to write int,double,float,char constants ConstantsTypeValue 12.45double12.45 12.45Ffloat12.45 0.5e-5double0.5*10 -5 12.75e3double12750.0 1234int1234 ’a’charSee Appendix A

7. TDBA66, VT-03 Lecture - Ch. 27 Assignment statements A variable can get its value via an assignment statement Ex. #definePI3.141596 int n; double radius, perimeter; n=10; radius=n*n+(n-1)/6; perimeter=2*PI*radius; Comment on evaluation order etc.(more on this in Ch. 3)

8. TDBA66, VT-03 Lecture - Ch. 28 Syntax of printf() printf(format string, print list); printf(format string); Ex. printf(”\nRadius is %f and perimeter”, radius); print(” is %10.2f\n”, perimeter); This is a prompting message or prompt printf(”Type radius in cm: ”); scanf(”%lf”, &radius); Read more about formating in section 2.5

9. TDBA66, VT-03 Lecture - Ch. 29 Syntax of scanf() scanf(format string, input list) Ex. int age; double weight; /* in kilogram */ printf(”Type your weight and age in one line: ”) scanf(”%lf%d”, &weight &age); Note &age denotes a pointer to (address to) the variable age

10. TDBA66, VT-03 Lecture - Ch. 210 Program Style Use spaces in the code Use comments in a clever way (say what the intention is) See Program Comment on page 49 in text book Read about Case Study on page 50

11. TDBA66, VT-03 Lecture - Ch. 211 Input/output redirection Instead of giving the input interactivly from the keyboard data can be taken from a file (text file) Ex. assume the executable file is called myprog Run by typing myprog myout_1 Now scanf() reads from myin_1 and printf() writes to myout_1 myin_1 should be a text file in the same directory as myprog Note! No prompting in the program in this case

12. TDBA66, VT-03 Lecture - Ch. 212 Program controlled Input/output from/to text files See page 59-61 for an overview but you can leave if for now (uses file pointers)

13. TDBA66, VT-03 Lecture - Ch. 213 Run-time errors When reading to char-varibles there is a risk that inputed characters ”hanging” in the input buffer will cause subsequent reading to fail See Fig. 2.13 page 65

14. TDBA66, VT-03 Lecture - Ch. 214 Figure 2.13 Function main for Disc Characteristics with Revised Beginning int main(void) { char part_id1, part_id2, /* input - 3-character part id */ part_id3; double radius, /* input - radius of disc in cm */ area, /* output - area of disc in cm^2 */ circum; /* output - circumference of disc (cm) */ /* Get the disc radius */ printf("Enter radius (in centimeters)> "); scanf("%lf", &radius); /* Get the part identifier */ printf("Enter a 3-character part i.d.> "); scanf("%c%c%c", &part_id1, &part_id2, &part_id3); /* Calculate the area */ area = PI * radius * radius; /* Calculate the circumference */ circum = 2 * PI * radius; /* Display the part i.d., area and circumference */ printf("For part %c%c%c, ", part_id1, part_id2, part_id3); printf("the disc area is %f cm^2.\n", area); printf("The circumference is %f cm.\n", circum); return (0); }