.T
and now a TEST
.R4C1
If we declare ~b~Ix~N to be an ARRAY of ~I6~N rows and ~I7~N columns, then:
.Q
The member of the ARRAY in row 3, column 3 is called
x[2][2]
~Inot~N x(2,2) or x(2)(2) or x[3,3) or etc. etc.
.Q
Which member does x+5*7+2 select ?
x[5][2]
.Q
Where does x point to ?
x is NOT a pointer!
( The names of ~I1~N-dimensional arrays are ~w~Rpointers~N.)
( Since, for example, ~b~Ix[2]~N is a 1-dim array, ~IIT~N is a ~w~Rpointer~N.)
.Q
x[3] points to which element ?
x[3][0]
.WN
0 ~b~I#include <stdio.h> ~N
1 ~b~Imain() { ~N
2 ~b~I char c; ~N
3 ~b~I while ( (c=getchar()) !='e' ) { ~N
4 ~b~I if ( 'a'<=c && c<='z') ~N
5 ~b~I printf("%c",c+'A'-'a'); ~N
6 ~b~I } ~N
7 ~b~I} ~N
.Q
If you type the letter p what will the program print ?
P
.Q
If you type the letter P what will the program print ?
P
.Q
What must you type to have the program stop ?
e
.WR9C1
.w
.R10C1
In Line 3, the program will ~b~Igetchar~N from the keyboard and assign it
to ~b~Ic~N. As long as ~b~Ic~N is NOT EQUAL to 'e' it enters the ~b~Iwhile~N loop.
In Line 4 it checks if ~b~Ic~N is a lower case 'a' to 'z'. If so, Line 5
is executed.
Line 5 will print the ~b~I%c~Nharacter whose 'value' is:
~Ithe value of c + the value of 'A' - the value of 'a'~N
If you type a ~b~Ip~N, the ASCII value is ~I112~N.
The ASCII value of 'A' is ~I65~N and for 'a' it's ~I97~N.
The value of ~b~Ic+'A'-'a'~N is ~I112+65-97~N which is ~I80~N, the ASCII
value for P ...so the program types a P ...and, in general, it converts
all lower case letters to upper case!
.WN
0 ~b~I#include <stdio.h> ~N
1 ~b~Imain(A,B) { ~N
2 ~b~Ichar B ~N
3 ~b~Iint A; ~N
4 ~b~Iprintf("%s",b[1]); ~N
5 ~b~I} ~N
.Q
How many errors ?
TOO MANY!
The arguments of ~b~Imain()~M MUST be declared ~Ibefore~N the opening ~b~I{~N.
The first argument is ALWAYS an ~b~Iint~N.
The second argument is ALWAYS a ~w~Rpointer~N to an ARRAY (of ~w~Rpointers~N).
Their IS a difference between B[1] and b[1] (Line 4).
Lastly (firstly?), Line 2 needs the !@#$% SEMI-COLON!
.W
0 ~b~I#include <stdio.h> ~N
1 ~b~Imain(A,B) ~N
2 ~b~Iint A; ~N
3 ~b~Ichar *B[]; ~N
4 ~b~I{ ~N
5 ~b~Iprintf("%s",B[1]); ~N
6 ~b~I} ~N
.WN
0 ~b~I#include <stdio.h> ~N
1 ~b~Imain(argc,argv) ~N
2 ~b~Iint argc; ~N
3 ~b~Ichar *argv[]; ~N
4 ~b~I{ ~N
5 ~b~I FILE *file_pointer, *fopen(); ~N
6 ~b~I file_pointer=fopen(argv[1],"r"); ~N
7 ~b~I} ~N
If the above program is compiled/linked under the name ~Isam~N, then
executed with the command:
~Isam george~N
.Q
what is the value of the integer argc ?
2
.Q
what string does argv[0] point to ?
sam
.Q
what string does argv[1] point to ?
george
.WN
0 ~b~I#include <stdio.h> ~N
1 ~b~Imain() { ~N
2 ~b~I char x[5]={'1','2','3','4','5'}; ~N
3 ~b~I char *y; ~N
4 ~b~I y=x; ~N
5 ~b~I printf("%s",x); ~N
6 ~b~I printf("%s",y); ~N
7 ~b~I} ~N
.Q
What does Line 5 print ?
12345è w
Since we forgot to terminate ~b~Ix[]~N with ~I'\0'~N, then ~b~Iprintf()~N
will start printing the characters, beginning with the ~Iaddress~N determined
by the ~r~Ipointer~N ~b~Ix~N, and continue ...and continue... until (finally)
it reaches a ~I0~N (somewhere in memory!) ...yielding lots of garbage!
.Q
What does Line 6 print ?
12345è w
In Line 4, the VARIABLE POINTER ~b~Iy~N is made to point to the same ~Istring~N
that ~b~Ix~N points to, so Line 6 prints the same 12345+garbage!
.WN
.T
That's all folks!
.K16,32
au revoir!
.q
