.T and now a TEST .R4C1 1 ~b~Imain() { ~N 2 ~b~I char key; ~N 3 ~b~I printf("\n Press a key "); ~N 4 ~b~I scanf("%c",key); ~N 5 ~b~I printf("\n You pressed %c",key);~N 6 ~b~I} ~N .Q Which line has the error? 4 Line ~I4~N should read: 4 ~b~I scanf("%c",~F&~N~b~Ikey); ~N .K19,60 Iknowthat! .WN 1 ~b~Imain() { ~N 2 ~b~I char key; ~N 3 ~b~I printf("\n Press a key "); ~N 4 ~b~I scanf("%c",&key); ~N 5 ~b~I printf("\n You pressed %c",key) ~N 6 ~b~I} ~N .Q Which line has the error? 5 Line ~I5~N should read: 5 ~b~I printf("\n You pressed %c",key)~F;~N .K19,60 ;;;;;;;;;; .WN .Q If x is an integer variable, then where in memory is it located? &x The ~Iaddress~N, in memory, of any variable ~b~Ix~N is ~b~I&x~N .K16,30 &x=address .R9C1 .Q &x is called a ? pointer .K16,30 pointertox .WN 1 ~b~Imain() { ~N 2 ~b~I int i; ~N 3 ~b~I char x='A'; ~N 4 ~b~I for (i=0; i<26; i++,x++) ~N 5 ~b~I printf("%c",x); ~N 6 ~b~I} ~N .Q How many errors can you find ? 0 .R8C60 ~INO ERRORS!~N .R11C1 4 ~b~I for (i=0; i<26; i++,~Fx++~N~b~I) ~N Although ~b~Ix~N is declared a ~b~Ichar~N and given the 'value' ~b~IA~N, the actual number stored in memory is (probably!) ~I65~N (in decimal) which is the ASCII value for an ~IA~N. This ~I65~N is incremented via ~b~Ix++~N and ~b~Iprintf()~N will print: ~r~IABCDEFGHIJKLMNOPQRSTUVWXYZ~N .K19,60 probably?? .W .R7C1B ~V DON'T TRUST THE INTERNAL COMPUTER 'VALUE' TO BE ASCII!! .W .R7C1B ~V however, if x is the 'A'-value, x+1 SHOULD be the 'B'-value...right? .WK8,30 RIGHT! .WN 1 ~b~Imain() { ~N 2 ~b~I printf("%s,%s,%s", ~N 3 ~b~I "Now is the time", ~N 4 ~b~I "for all good me", ~N 5 ~b~I "n to come to th", ~N 6 ~b~I "e aid of thier ", ~N 7 ~b~I "country."; ~N 8 ~b~I} ~N .Q How many errors here? 2 ~V  i-before-e-except-after-c ? ~N .R6C1 6 ~b~I "he aid of ~Fthier~N~b~I", ~N .K2,50 their .WR14C1 ...and the printout would be: ~r~INow is the timefor all good men to come to the aid of thier country.~N  tch!tch! .WN 1 ~b~Imain() { ~N 2 ~b~I int w; ~N 3 ~b~I char z='z'; ~N 4 ~b~I w=z; ~N 5 ~b~I while (z>'w'); ~N 6 ~b~I printf("%c=%d;",z--,w--);~N 7 ~b~I} ~N .Q Which line has the error ? 5 Line 5 shouldn't have a semi-colon! (NOT after ~Iwhile~N or ~Ifor~N): .R5C1 5 ~b~I while (z>'w')~F;~N~b~I ~N .WK2,50 z--,w--??? .R14C1 Line 4 sets ~b~Iw~N to the ~Ivalue~N of ~b~Iz~N ( 122 in ASCII ). Line 6 is executed, ~b~Iprintf~N-ing the ~b~I%c~Nhar ~b~Iz~N and the ~b~I%d~Necimal ~b~Iw~N, then both ~b~Iz~N and ~b~Iw~N are ~IDECREMENTED~N (via ~b~Iz--,w--~N), and line 6 is repeated ...as long as ~b~I%c~Nharacter ~b~Iz~N is greater than ~b~I'w'~N (meaning the 'value' of ~b~Iz~N exceeds the 'value' of the character ~b~Iw~N, which, in ASCII, is 119). .W The printout would be: ~r~Iz=122;y=121;x=120;~N .WK2,50 confusing! .WN 1 ~b~Imain() { ~N 2 ~b~I char s; ~N 3 ~b~I s="I'm a string"; ~N 4 ~b~I printf("%s",&s); ~N 5 ~b~I} ~N .Q Which line has the error(s) ? 4 Line 4 should be: 4 ~b~I printf("%s",s); ~N ...without the ~b~I&~N ! .R13C1 Although ~b~Iprintf()~N expects to recieve the ~Iaddress~N of a ~b~I%s~Ntring variable (such as ~b~Is~N), we must ~V let C do it~N! We just refer to ~b~Is~N, in ~b~Iprintf("%s",s)~N, and the C-compiler will look after passing the address to ~b~Iprintf()~N. .W .R13C1 Although ~b~Iprintf()~N expects to ~Frecieve~N the ~Iaddress~N of a ~b~I%s~Ntring .K2,50 sorry! .WR13C1 Although ~b~Iprintf()~N expects to receive the ~Iaddress~N of a ~b~I%s~Ntring .R18C1 The printout might be: ~r~IìI~N ...or some other garbage! .WNT single CHARacters and INTegers are the same ? .R4C1 1 ~b~Imain() { ~N 2 ~b~I char x; ~N 3 ~b~I for (x=0; x<=255; x++) ~N 4 ~b~I printf("%c",x); ~N 5 ~b~I} ~N .Q Will this print the IBM PC character set ..once ? n When we increment ~b~Ix~N from ~b~I0~N to ~b~I255~N we ~IDO~N get a printout of the ~b~I%c~Nharacters whose 'values' are ~I0~N, ~I1~N, ~I2~N, etc. BUT, because a ~b~I%c~Nharacter ~IALWAYS~N occupies a single byte in memory their 'values' are ~IALWAYS~N ~b~I<=255~N (less-than-or-equal-to 255). SO ...incrementing ~b~Ix~N, when it has the 'value' ~I255~N, will give the 'value' ~b~I0~N ...and the above program will continue to cycle through the character set ...forever! .K4,65 forever? .W 1 ~b~Imain() { ~N But ~Ithis~N program WILL stop 2 ~b~I int x; ~N when the ~b~I%int~Neger ~b~Ix~N 3 ~b~I for (x=0; x<=255; x++) ~N reaches the value ~I256~N, since 4 ~b~I printf("%c",x); ~N ~b~Iint~Negers CAN be larger than ~I255~N 5 ~b~I} ~N .K4,65 int is big .WN 1 ~b~Imain() { ~N 2 ~b~I float x, y; ~N 3 ~b~I printf("Enter two numbers); ~N 4 ~b~I scanf("%f%f",x,y); ~N 5 ~b~I printf("%s%f", ~N 6 ~b~I "Their sum is ", ~N 7 ~b~I sum(x,y); ~N 8 ~b~I} ~N 9 ~b~Isum(a,b) ~N 10~b~I{ ~N 11~b~Ifloat a, b; ~N 12~b~Ireturn(a+b); ~N 13~b~I} ~N .Q How many BUGS!@#$ ??? 4 .WR18C1 Forgot something in line 3.... .R3C38 ~b~I printf("Enter two numbers~F"~N~b~I); ~N .WR18C1 Forgot something in line 7 too! .R7C38 ~b~I sum(x,y)~F)~N~b~I; ~N .WR18C1 Forgot to declare the function type (else we'd get ~Iintegers~N returned!) .R9C38 ~b~I~Ffloat~N~b~I sum(a,b) ~N .WR18C1 .R18C1 We ~IMUST~N declare function arguments ~IIMMEDIATELY~N (~Ibefore~N the ~b~I{~N)! .R10C38 ~b~Ifloat a, b; ~N wrong .R11C38 ~b~I{ ~N order .WN 1 ~b~Imain() { ~N 2 ~b~I int words=0; ~N 3 ~b~I char c; ~N 4 ~b~I while ( (c=getchar())!='\r' && c!='\n') }~N 5 ~b~I if (c == ' ') ~N 6 ~b~I words++; ~N 7 ~b~I } ~N 8 ~b~I printf("\n Number = %d",words); ~N 9 ~b~I} ~N .Q Any errors here (y/n) ? n .R10C60 ~INO ERRORS~N .R4C1 4 ~b~I while ( (~Vc=getchar()~N~b~I)!='\r' && c!='\n') }~N .R13C1 Here we invoke the C-library function ~b~Igetchar()~N which inputs a ~Isingle~N character, which we assign to our ~b~Ichar~Nacter variable ~b~Ic~N. .WR4C1 4 ~b~I while ( (c=getchar())~V!='\r' && c!='\n'~N~b~I) }~N .R13C1 .R13C1 Here we check to see that the ~b~Ic~Nharacter is NOT EQUAL (~b~I!=~N) to a ~b~I\r~Neturn AND (~b~I&&~N) NOT EQUAL to a ~b~I\n~Newline. ( This then will exit the ~b~Iwhile~N loop when we press the ~IEnter~N key ). As long as it's NOT EQUAL, we execute the ~b~Iwhile~N loop. .K2,60 &&=AND !! .WR4C1 4 ~b~I while ( (c=getchar())!='\r' && c!='\n') }~N 5 ~V if (c == ' ') ~N 6 ~V words++; ~N .R13C1 .R13C1 Inside the ~b~Iwhile~N, we check if the ~b~Ic~Nharacter ~b~I== ' '~N (~IEQUAL~N a space) and, if it is, we increment the ~b~Iint~Neger ~b~Iwords~N. .WR5C1 5 ~b~I if (c == ' ') ~N 6 ~b~I words++; ~N 7 ~V } ~N .R13C1 .R13C1 The first time that the ~IEnter~N key ~b~Ic~Nharacter occurs, we exit the ~b~Iwhile~N loop ...and this ~b~I}~N defines the ~Iend-of-the-while~N. .WR7C1 7 ~b~I } ~N 8 ~V printf("\n Number = %d",words); ~N .R13C1 .R13C1 After leaving the ~b~Iwhile~N, we ~b~Iprintf()~N the value of ~b~Iwords~N, which may (or may not!) agree with the number of 'words' typed. (It WILL if you ~Ifollow~N every word with ~Ione~N space!) .WR8C1 8 ~b~I printf("\n Number = %d",words); ~N 9 ~V} ~N .R13C1 .R13C1 ...and the end of ~b~Imain()~N ( = end of the program! ) .WR15C1 If we compiled/linked/ran this program, we'd get: ~VThis is a line which has 7 words ~N You type this, and press ~IEnter~N. ~r~I Number = 8~N The computer responds thus! .WK2,60  SMART! .WN Suppose we have 3 ~b~Ichar~Nacter variables: ~b~Ix='A' ; y='a' ; z='B'~N .Q Is x!=y (y/n)? y .Q Is x!=z (y/n)? y .Q Is x!=x (y/n)? n .Q Is x!=y && x!=z (y/n)? y .WR15C1 Since x ~IIS~N different from y, the first answer is ~Iy~N. Since x ~IIS~N different from z, the second answer is ~Iy~N. Since x ~IIS NOT~N different from x, the third answer is ~In~N. Since x ~IIS~N different from y ~IAND~N x ~IIS~N different from z the fourth answer is ~Iy~N. .WN 0 ~b~I#include ~N 1 ~b~Imain() { ~N 2 ~b~Ifloat x=34.56; ~N 3 ~b~Iprintf("%6.1f",x); ~N 4 ~b~Iprintf("%-6.1f",x); ~N 5 ~b~Iprintf("%06.1f",x); ~N 6 ~b~I} ~N .Q What will be printed in Line 3 ? 34.6 .Q What will be printed in Line 4 ? 34.6 .Q What will be printed in Line 5 ? 0034.6 .WN .Q A C-expression meaning: n=n+1 n++ .Q Another C-expression meaning: n=n+1 ++n .Q A C-expression meaning: n=n+5 n+=5 .Q A C-expression meaning: n=n/7 n/=7 .Q A C-expression meaning: n=n-2 n-=2 .Q A C-expression meaning: n=n*9 n*=9 .WN ~b~I if ( (x IS GREATER THAN 5) AND (x IS NOT EQUAL TO 7) ) ~N ~b~I if ( x IS EQUAL TO 9 ) ~N .Q What C operator should replace IS GREATER THAN ? > .Q What C operator should replace AND ? && .Q What C operator should replace IS NOT EQUAL TO != .Q What C operator should replace IS EQUAL TO == .WN 1 ~b~Imain() { ~N 2 ~b~Iint i; ~N 3 ~b~Ifloat x; ~N 4 ~b~Ii=5.2; ~N 5 ~b~Ix=i/2; ~N 6 ~b~Iprintf("%f",x); ~N 7 ~b~I} ~N .Q What will be printed ? 2.000000 In line 4, ~b~I5.2~N (a ~b~Ifloat~N) is converted to an ~b~Iint~N 'cause ~b~Ii~N is declared to be an ~b~Iint~N in Line 2, so the number ~I5~N is assigned to ~b~Ii~N. In Line 5, because both ~b~Ii~N and ~b~I2~N are ~b~Iint~Negers ( no decinal in ~b~I2~N, remember?), the division gives ~I5/2~N without the decimal part, ~I2~N, which is then converted to ~b~Ifloat~N ('cause ~b~Ix~N is a ~b~Ifloat~N) and assigned to ~b~Ix~N ....and ~b~Iprintf()~N gives 6 decimal places (unless told otherwise!). .WN .T That's all folks! .K16,32 au revoir! .q