1 / 31

Lecture 13 Transition from Fortran to C

Lecture 13 Transition from Fortran to C. Yi Lin Feb 27, 2007. PROGRAM hello IMPLICIT NONE !This is my first program WRITE (*,*) “Hello World!“ END PROGRAM hello. int main() { printf( “Hello World!<br>”); return 0; }. Hello World!. C is space insensitive but case sensitive.

onawa
Download Presentation

Lecture 13 Transition from Fortran to C

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. Lecture 13 Transition from Fortran to C Yi Lin Feb 27, 2007

  2. PROGRAM hello IMPLICIT NONE !This is my first program WRITE (*,*) “Hello World!“ END PROGRAMhello int main() { printf( “Hello World!\n”); return 0; } Hello World! C is space insensitive but case sensitive. \>gfortran hello.f90 \>gfortran hello.f90 –o hello \>hello \>gcc hello.c \>gcc hello.c –o hello \>hello

  3. Programming language in general • Variable, expression, statement • Conditional statement (if-else) • Iteration statement (loop) • Sub-program units (functions) T F Log Exp 1st Block 2nd block F i < n T 1st Block

  4. INTEGER REAL CHARACTER int short long unsigned int unsigned short unsigned long float double char Comparison of Fortran and C, variable types

  5. Variable size in C

  6. What is the difference from a Fortran program? int main(){ int a, b, c, d; unsigned u; a=12; b=-24;u=10; c=a+u; d=b+u; printf(“a+u=%d, b+u=%d\n”, c, d); return 0; } OUTPUT: a+u=22, b+u=-14 PROGRAM test IMPLICIT NONE INTEGER::a,b,c,d,u a=12 b=-24 u=10 c=a+u d=b+u WRITE(*,*) “a+u=“,c, “b+u=“,d END PROGRAM test Example 2: int

  7. Example 3: double int main(){ double x; int i; x=3.6; i=(int)x; //Force type casting from double to int. Not int(x) /* (int)x+i: force x to an int and then plus i */ printf(“x=%f, i=%d”, x, i); // x doesn’t change return 0; } OUTPUT: x=3.600000, i=3

  8. Example 4: char and string int main(){ char c1, c2; char* str; // more about “*” in the next class. c1=‘a’; c2=‘b’; printf(“c1=%c, c2=%c\n”, c1, c2); c1=97; c2=98; // In ASCII codes, a-z: 97-123, A-Z:65-91 printf(“c1=%c, c2=%c\n”, c1, c2); c1 = c1 - 32; c2 = c2 - 32; // equivalent to: c1 -=32; c2 -=32; printf(“c1=%c, c2=%c\n”, c1, c2); str = “Hello world!”; printf(“str=%s\n”, str); return 0; } OUTPUT: c1=a, c2=b c1=a, c2=b c1=A, c2=B str=Hello world!

  9. Arithmetic Operators • Arithmetic operators • ++, --, -(minus) right to left • *, /, % left to right • +, -(sub) left to right • post-, pre-, Incrementing(++), decrementing(--) i++ After using i, increasing i by 1 i-- After using i, decreasing i by 1 ++i Before using i, increasing i by 1 --i Before using i, decreasing i by 1 high low

  10. Example 5: ++, -- int main(){ int i, j; i=3; j=++i; printf(“i=%d, j=%d\n”, i,j); // output: i=4,j=4 i=3; j=i++; printf(“i=%d, j=%d\n”, i,j); // output: i=4,j=3 i=3; j=--i; printf(“i=%d, j=%d\n”, i,j); // output: i=2,j=2 i=3; j=i--; printf(“i=%d, j=%d\n”, i,j); // output: i=2,j=3 return 0; }

  11. Example 6: ++, -- int main(){ int i, j; i=3; printf(“i=%d\n”, ++i); //Output: i=4 j=i++; printf(“i=%d, j=%d\n”, i,j); //Ouput:i=5, j=4 i=3; printf(“i=%d\n”, i++); //Output: i=3 j=i++; printf(“i=%d, j=%d\n”, i,j); //Ouput:i=5, j=4 return 0; }

  12. Operators (cont.) • Relational operators • ==, != (eqv. to /= in Fortran), <, <=, >, >= • Logical operators • ! (eqv. to .NOT. in Fortran) R to L • && (eqv. to .AND. in Fortran) L to R • || (eqv. to .OR. in Fortran) L to R • Bitwise operators (Not required!) • &, |, ^, ~, <<, >> high low

  13. Operators (cont.) • Ternary operator • <logical-exp> ? <exp1> : <exp2> • If the logical-exp is true, the value of this expression is exp1’s value, otherwise, it is the value of exp2. • Example 7: int main(){ int i, j; scanf(“%d”, &i); // eqv to READ(*,*) in Fortran j=(i>0) ? i : -i; // if i is positive j=i, otherwise, j=-i printf(“i=%d, j=%d\n”, i, j); return 0; } READ in value: -5 OUTPUT: i=-5, j=5

  14. Operators (cont.) • Condensed operators • +=, -=, *=, /=, %= • E.g. a += b; // eqv. to a=a+b • &=, |=, ^=, <<=, >>= (Not. Required!) Example 8: int main(){ int i, j; i=2; j=3; i+=j; printf(“i=%d, j=%d\n”, i, j); //output: i=5, j=3 i=2; j=3; i-=j; printf(“i=%d, j=%d\n”, i, j); //output: i=-1, j=3 i=2; j=3; i*=j; printf(“i=%d, j=%d\n”, i, j); //output: i=6, j=3 i=2; j=3; i/=j; printf(“i=%d, j=%d\n”, i, j); //output: i=0, j=3 i=2; j=3; i%=j; printf(“i=%d, j=%d\n”, i, j);//output: i=2, j=3 return 0; }

  15. scanf and printf • Syntax: • scanf(<formats>, <list of variables>); • printf(<formats>, <list of variables>); • Formats: • d: decimal int • o: octal int • x: hexdecimal int • c: character • s: string • f: real number, floating point • e: real number, exponential format

  16. Example 9: scanf and printf int main(){ int a, b, c; scanf(“%d%d%d”, &a, &b, &c); printf(“%d, %d, %d\n”, a, b, c); return 0; } Valid input: 3#4#5  3, 4, 5 3##4###5  3, 4, 5 3 4#5  3, 4, 5 3<TAB>4<TAB>5  3, 4, 5 Invalid input: 3,4,5

  17. int main(){ // example 10 int a, b, c; scanf(“%d,%d,%d”, &a, &b, &c); printf(“%d, %d, %d\n”, a, b, c); return 0; } Valid input: 3,4,5  3, 4, 5 3,#4,##5  3, 4, 5 int main(){ // example 11 int a, b, c; scanf(“%d:%d:%d”, &a, &b, &c); printf(“%d, %d, %d\n”, a, b, c); return 0; } Valid input: 3:4:5  3, 4, 5 3:#4:##5  3, 4, 5 Example 10, 11: scanf and printf It doesn’t matter if written in one line.

  18. Example 12: scanf and printf int main() { float a, b; double c,d; scanf(“%f%f%lf%lf”, &a, &b, &c, &d); // %lf for double, %ld for long int printf(“a=%f, b=%6.2f, c=%f, d=%6.2f”, a, b, c, d); /* 6.2f: output b with 6 digits width and 2 decimal digits */ return 0; } Valid input: 1.3##2.4#3.5#6.2  a=1.300000, b=##2.40, c=3.500000, d=##6.20

  19. Example 13: scanf and printf int main() { int a, b; scanf(“%3d%3d”, &a, &b); printf(“a=%4d, b=%4d\n”, a, b); return 0; } Valid input: 123456  a=123, b=456 12#34#  a=12, b=34

  20. if (logical-exp) statement if (logical-exp) statement1 else statement2 IF (logical-exp) statement IF (logical-exp) THEN 1st block of statements ELSE 2nd block of statements END IF Conditional statement

  21. int main(){ int i; scanf(“%d”, &i); if(i<0) printf(“%d”, i); else printf(“%d”, -i); return 0; } PROGRAM test IMPLICIT NONE INTEGER::i READ(*,*) i IF(i<0) THEN WRITE(*,*) i ELSE WRITE(*,*) –i END IF END PROGRAM test Example 14: if, if-else What if there are more than 1 statement between if and else? INPUT: -5 OUTPUT: 5

  22. int main() { int a, b, t=0; scanf(%d,%d”,&a,&b); if(a>b) t=a; a=b; b=t; printf(“%d %d %d\n”, a, b, t); return 0; } PROGRAM test INTEGER::a, b, t=0 READ(*,*) a, b IF(a>b) THEN t=a a=b b=t END IF WRITE(*,*) a, b END PROGRAM test Example 15: scope {} int main() { int a, b, t=0; scanf(%d,%d”,&a,&b); if(a>b){ t=a; a=b; b=t; } printf(“%d %d %d\n”, a, b, t); return 0; } INPUT: 3, 1 OUTPUT: 1 3 3 INPUT: 1, 3 OUTPUT: 1 3 0 PROGRAM test INTEGER::a, b, t=0 READ(*,*) a, b IF(a>b) & t=a a=b b=t WRITE(*,*) a, b END PROGRAM test INPUT: 3, 1 OUTPUT: 1 3 3 INPUT: 1, 3 OUTPUT: 3 0 0

  23. Example 16: if-else if-else • Problem: write a program to read an integer x and output the corresponding y: int main() { int x, y; scanf(“%d”, &x); if(x<0) y=-1; else if(x==0) y=0; else y=1; printf(“x=%d,y=%d\n”, x, y); return 0; }

  24. int main() { char grade; scanf(“%c”, &grade); switch (grade){ case ‘A’: printf(“85~100”\n”); break; case ‘B’: printf(“70~84\n”); break; case ‘C’: printf(“60~69\n”); break; case ‘D’: printf(“<60\n”); break; default: printf(“error\n”); } return 0; } PROGRAM test IMPLICIT NONE CHARACTER::grade READ(*,*) grade SELECT CASE (grade) CASE ‘A’: WRITE(*,*) “85~100” CASE ‘B’: WRITE(*,*) “70~84” CASE ‘C’: WRITE(*,*) “60~69” CASE ‘D’: WRITE(*,*) “<60” DEFAULT: WRITE(*,*) “error” END SELECT END PROGRAM Switch case, example 17 “break” is very important! Without it, if grade==‘A’, output: 85~100 70~84 60~69 <60 error

  25. C (i<n as an example logical-exp) while(i<n) { <loop body> i++; } do { <loop body> i++; } while(i<n); for(i=1; i<n; i++){ <loop body> } Fortran (i<n as an example logical-exp) DO count=1, n, 1 <loop body> END DO DO IF(i>n) EXIT <loop body> i=i+1 END DO DO WHILE(i<n) <loop body> i=i+1 END DO ITERATION

  26. int main(){ // example 18 int i, sum=0; i=1; while(i<=10){ sum +=i; // eqv. to sum=sum+i; i++; // eqv. to i=i+1; or ++i; } prinf(“sum=%d\n”,sum); return 0; } int main(){ // example 19 int i, sum=0; i=1; do { sum +=i; // eqv. to sum=sum+1; i++; // eqv. to i=i+1; or ++i; } while(i<=10) ; prinf(“sum=%d\n”,sum); return 0; } Example 19: do while

  27. int main(){ // example 20 int i, sum=0; scanf(“%d”, &i); while(i<=10){ sum +=i; // eqv. to sum=sum+i; i++; // eqv. to i=i+1; or ++i; } prinf(“sum=%d\n”,sum); return 0; } int main(){ // example 21 int i, sum=0; scanf(“%d”, &i); do { sum +=i; // eqv. to sum=sum+i; i++; // eqv. to i=i+1; or ++i; } while(i<=10); prinf(“sum=%d\n”,sum); return 0; } Example 20: while v.s. do-while INPUT: 1 OUTPUT: 55 INPUT: 11 OUTPUT: 11 INPUT: 1 OUTPUT: 55 INPUT: 11 OUTPUT: 0

  28. int main(){ // example 22 int i, sum=0; for(i=1; i<=10; i++) { sum+=i; } printf(“sum=%d\n”,sum); return 0; } Syntax for(exp1; log-exp2; exp3) statement(s) for: example 22 exp1 F Log-exp2 T statement(s) exp3

  29. // Same as example 22 int main(){ // example 23 int i, sum=0; i=1; for(; i<=10; i++) { sum+=i; } printf(“sum=%d\n”,sum); return 0; } // Same as example 22 int main(){ // example 24 int i, sum; i=1; for(sum=0; i<=10; i++) { sum+=i; } printf(“sum=%d\n”,sum); return 0; } Example 23, 24: for

  30. // Same as example 22 int main(){ // example 25 int i, sum; for(i=1, sum=0; i<=100; i++) { sum+=i; } printf(“sum=%d\n”,sum); return 0; } // Same as example 22 int main(){ // example 26 int i, sum=0; i=1; for(; i<=100; ) { sum+=i; i++; } printf(“sum=%d\n”,sum); return 0; } Example 25,26: for

  31. int main(){ // example 27 int i; for(i=1; i<10; i++){ if(i == 8) break; // Loop terminated when i==8 printf(“%d\n”, i) //write numbers 1 to 7 only } return 0; } PROGRAM test DO i=1,10 if(i == 8) EXIT !Loop terminated when i==8 WRITE(*,*) i !write numbers 1 to 7 only END DO END PROGRAM Example 27: break “continue” is similar.

More Related