1 / 21

Introduction to Systems Programming - Recitation

Introduction to Systems Programming - Recitation. Omer Kotlicki E-Mail: omerkot@gmail.com Two instances: Tuesdays 15:00-16:00; Kitot 206 Wednesdays 11:00-12:00; Kitot 206 Reception: Wednesdays 12:00-13:00 - room #32 at the nano center (under the library). Administrivia.

elijah-logan
Download Presentation

Introduction to Systems Programming - Recitation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Introduction to Systems Programming - Recitation • Omer Kotlicki • E-Mail: omerkot@gmail.com • Two instances: • Tuesdays 15:00-16:00; Kitot 206 • Wednesdays 11:00-12:00; Kitot 206 • Reception: • Wednesdays 12:00-13:00 - room #32 at the nano center (under the library)

  2. Administrivia Course home page: http://www.eng.tau.ac.il/~isp Course Mailing list: http://listserv.tau.ac.il/archives/eng0512-4402-01.html Books Modern Operating Systems, 3rd edition, by Tanenbaum. Prentice-Hall, 2008. 2nd edition (2001) is fine too. Grades Final exam 65% Exercises 35% Avishai Wool Lecture 1 - 2

  3. Administrivia – cont. Significant programming in C 3-4 exercises + final project Windows programming environment (Microsoft VC++ / Visual Studio) Assignments in pairs Sharing / copying exercises will NOT be tolerated Avishai Wool Lecture 1 - 3

  4. About the Crash Course • Created by Prof. Cooperstock from McGill University, Montreal • Cover sufficient C for simple programs: • variables and statements • control • functions • arrays and strings • pointers • Slides and captured lecture (video and sound) are available at: • http://www.cim.mcgill.ca/~jer/courses/C/

  5. Why C? • C is not always a good choice ... • Safety-critical systems • Component-based programming / RAD • ... • ... but in many applications you do want C • Legacy systems • Speed, memory requirements • Low-level programming (close to the machine) • ...

  6. Your First C Program • "The only way to learn a new programming language is by writing programs in it" [K&R] • /* A simple program that prints something */ • #include <stdio.h> • main () • { • printf ("Hello, world!\n"); • }

  7. Declarations • Example: • float x; • double d = 5; • int *p, i, a[100]; • char s[21]; • Syntax: • type variable_name, ... [= value]; • Rules: • declarations must precede executable statements • int type may be modified by: long, short, unsigned

  8. Changing Variable Values • Example: • int x, y, z; • x = 2; • x = x + 1; • Getting Fancy • y = z = 4 + 5; • x += 1; • ++x; • x++; • y = x--; • Note: • assignment statements return value, which may or may not be ignored; same goes for increment statements

  9. Formatted Output • Example: • int i = 10; • float f = 2.5; • char s [] = "hi"; • printf ("Jack\'s integer is %d\n", i); • printf ("Jill\0x27s float is %f\n", f); • printf ("My string s = %s\n", s); • Syntax: • printf (string_with_formatting, var1, var2, ...); • Formats: %d integer, %f float, %c character, %s string, … • Note "escape sequences": \n newline, \' quote, \0x27, etc. • #include <stdio.h> is compulsory; more about it later

  10. Formatted Input • Example: • #include <stdio.h> • int i; • float f; • scanf ("%d %f\n", &i, &f); • /* inputs an integer and a float */ • Syntax: • scanf (string_with_formatting, &var1, &var2,...); • Note: • The ampersand (&) is necessary because scanfmodifies the values stored in the respective variables; by comparison, printf only uses the values, without modifying them. More about this later

  11. I/O Example • What does this print? • #include <stdio.h> • main () • { • int n; • float x; • char mark; • scanf ("%d %f %c", &n, &x, &mark); • printf ("Of %d %s,\n%f got %c\’s\n", • n, "students", x, mark); • } • Type in the following input: 86 85.999 A

  12. I/O Example • #include <stdio.h> • main () • { • int n; • float x; • char mark; • scanf ("%d %f %c", &n, &x, &mark); • printf ("Of %d %s,\n%f got %c\’s\n", • n, "students", x, mark); • } • Input: • 86 85.999 A • Output: • Of 86 students, • 85.999001 got A's

  13. Conditional Statements • Example: • if (age < 0) • { • printf ("warning: negative age\n"); • age = -age; • } • Syntax: • if (condition) statement • if (condition) statement else statement • Rules: • the condition is an int ! (no booleans) • parentheses required around conditional expression • use curly braces to make a compound statement

  14. More Conditionals • Example: • if (x < 0) • printf ("x is less than 0\n"); • else if (x == 0) • printf ("x is equal to 0\n"); • else • printf ("x is greater than 0\n"); • What’s wrong with this? • if (x < 0) • if (y < z) • printf ("y is less than z\n"); • else • printf ("x not less than 0\n");

  15. While Loops • Example: • /* print "hi" forever */ • while (1) • printf ("hi"); • Syntax: • while (condition) • statement • Rules (again): • the condition is an int ! (no booleans) • parentheses required around conditional expression • use curly braces to make a compound statement

  16. For Loops • Example: • /* print "hi" three times */ • int i; /* i continues to exist when loop ends */ • for (i = 0; i < 3 ; i++) • printf ("hi"); • Syntax: • for (statement1; condition; statement2) • statement3; • Equivalent to: • statement1; • while (condition) { • statement3; • statement2; • }

  17. Loop Example • /* print squares up to 100 */ • main ( ) • { • int j, up = 100; • for (j = 0; j * j <= up; j++) • printf ("%d \n", j * j); • } • Note: • can’t do: for (int j = 0; ... • waste of one multiplication per iteration • can you make it more efficient?

  18. Example (cont’d) • /* print squares up to 100 */ • void main ( ) • { • int j, up = 100, sq; • for (j = 0; (sq = j * j) <= up; j++) • printf ("%d \n", sq); • } • Note: • recall equivalence to a while loop: condition is evaluated before the loop body

  19. Arrays • int years[45]; • float temperatures [11]; • void main () { • years[0] = 2000; • temperatures[11] = -45.67; • } • Rules: • indices start at zero • maximum valid index is the size of the array minus 1 • but C lets you go beyond the declared boundaries • temperatures[11] is illegal

  20. Characters • Characters • char a, b, c1, c2; • a = '0'; b = '\037'; c1 = 'K'; c2 = c1 + 1; • Assigns values: 48, 31, 75, 76 • The sequences '0',...,'9', 'a',...,'z', 'A',...,'Z' contain characters numbered consecutively • Casting • printf ("%c %d\n", c1, (int) c1); • Outputs: K 75

  21. Strings • Strings are '\0'-terminated arrays of char : • char s[3] = "hi"; /* invisible '\0' */ • char t[3] = {'h', 'i', '\0'}; • String operations • #include <string.h> • strlen ("there"); /* returns 5 */ • strcpy (s, t); /* copy t to s */ • strcmp (s, t) /* alphabetical comparison */

More Related