These problems are provided to you as a guide for practice. The questions cover important concepts covered in class.

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1 Midterm Written Exam Practice Midterm will cover all concepts covered up to the midterm exam. Concepts of arrays, LL s, pointers (*,**,***), malloc, calloc, realloc, function pointers, Hash tables will be included in the midterm. Midterm is 80 minutes long. The question types include, multiple choice, code debugging, code tracing, completing functions etc. More will be discussed in class. Here are some code debugging questions. These problems are provided to you as a guide for practice. The questions cover important concepts covered in class. Important Types of Errors Programs typically generate number of different types of errors. You must be able to sort through these errors to figure out what is wrong with a program. Here are some types of errors We will discuss each one of these errors in detail in class. We will also give examples. Here are some problems to try based on these errors. Each one of these problems either produce the correct output or gives an error OR if the program crashes, then give The first line number where the program is likely to crash, die, or express an incorrect result The single best description of the underlying, root cause of the problem. (Not a description of the defective behavior that is exhibited) Questions are courtesy of Tim Hoffman

2 /* QUESTION #1 10 PTS*/ int * getint() int val; printf("enter a number: "); scanf("%d", &val); return( &val ); int * pi; pi = getint(); printf("you entered: %d\n", *pi ); /* QUESTION #3 10 PTS */ #define MAXLEN 5 int i, *curr1, *curr2; int * arr1 = malloc( MAXLEN * sizeof(int) ); int * arr2 = malloc( MAXLEN * sizeof(int) ); arr2[i] = i*2; curr1 = arr1; curr2 = arr2+maxlen-1; while (curr2 >= arr2) *(curr1++) = *(curr2--); printf("%d ", arr1[i] ); printf("\n"); printf("%d ", arr2[i] ); free(arr1); free(arr2);

3 /* QUESTION #4 10 PTS */ #define MAXLEN 10 int * arr = malloc( MAXLEN * sizeof(int) ); arr[i] = i*2; printf("%d ", *(arr++) ); free(arr); /* QUESTION #5 10 PTS*/ void Question5(char **wordarray) char **x; wordarray = calloc(10, sizeof(char*)); x=wordarray; for(i=0; i<10; i++) *(x++) = calloc(10, sizeof(char)); strcpy(wordarray[0], "This"); strcpy(wordarray[1], "is"); strcpy(wordarray[2], "a"); strcpy(wordarray[3], "test."); int main( int argc, char *argv[])

4 char **words; Question5(words); printf("question 10: "); for (i=0; i<10; i++) printf("%s", words[i]); printf("\n"); /* QUESTION #6 10 PTS */ #define MAXLEN 10 int main(int argc, char *argv[] ) int array[ MAXLEN ]; *(array+i) = i; printf( "%d ", *(array+i) ); free (array); /* QUESTION #7 */ #define MAXLEN 10 int main(int argc, char *argv[] ) int *array = malloc( MAXLEN * sizeof(int) );

5 *(array+i) = i; printf( "%d ", *array ); ++array; free (array); /* QUESTION #8 10 PTS*/ int *willy = malloc( 5 * sizeof(int) ); int *willyslast = bar + 4; for (i=0 ; willy<=willyslast; ++willy,++i) *willy = i; /* print willy */ for (i=0 ; i<5 ; ++i) printf("%d ", willy[i] ); free( willy ); /* QUESTION #9 10 PTS*/ How can I declare an array of ints with 5 elements in the array? (circle any/all that apply) a) int arr[5]; b) #define MAX 5

6 int arr[max]; c) int *arr = 1,2,3,4,5 ; d) int *arr = malloc( 5*sizeof(int) ); e) all of the above /* QUESTION #10 10 PTS 2 pts each */ assume: int * x = 1,1,2,4,5; a) What does the expression x+4 produce? b) What does the expression x produce? c) What does the expression &x produce? d) What does the expression *x produce? e) What does the expression *(x+2) produce? ANSWERS TO ABOVE QUESTIONS IN PRACTICE-II-SOL.PDF EXTRA QUESTIONS Question #1 #include <stdlio.h> char * getword( char * prompt, char * word ) printf("%s", prompt ); scanf("%s", word ); /* ASSUME USER ENTERS "FOOBAR" */ return word; int main() char * word; word = getword("enter a word: ", word ); printf("you entered: %s\n", word );

7 Question #2 char * getword( char * prompt, char * word ) printf("%s", prompt ); scanf("%s", word ); /* ASSUME USER ENTERS "FOOBAR" */ return word; int main() char * word = (char*) malloc( 20 ); word = getword("enter a word: ", word ); printf("you entered: %s\n", word ); free(word); Question #3 #include #include char * getword( char * prompt, char * word ) word = (char*) malloc( 20 ); printf("%s", prompt ); scanf("%s", word ); /* ASSUME USER ENTERS "FOOBAR" */ return word; int main() char * word; word = getword("enter a word: ", word ); printf("you entered: %s\n", word ); free(word);

8 Question #4 #include <stdlio.h> void getword( char * prompt, char * word ) word = (char*) malloc( 20 ); printf("%s", prompt ); scanf("%s", word ); /* ASSUME USER ENTERS "FOOBAR" */ int main() char * word; getword("enter a word: ", word ); printf("you entered: %s\n", word ); Question #5 struct Foo int data; struct Foo *next; ; typedef struct Foo Foo; int main() Foo * tmp; Foo * head = (Foo *) NULL; for ( i=0 ; i < 5 ; ++i ) tmp = (Foo*) malloc( sizeof( Foo) ); tmp->data = i; tmp-&gtnext = head; head = tmp; for( tmp=head ; tmp ; tmp=tmp->next) printf("%d ",tmp-&gtdata);

9 Question #6 Assume this declaration: int * arr[5]; Which diagram best describes memory allocation? (CIRCLE ANSWER) a) arr: [0][0][0][0][0] b) arr: [NULL][NULL][NULL][NULL][NULL] c) arr: [int*][int*][int*][int*][int*] < d) arr: [5] Question #7 Assume this declaration: int ** arr; Which diagram best describes memory allocation? (CIRCLE ANSWER) a) arr: [int**] b) arr: [int*] --> [int*] c) arr: [int*] --> [int] d) arr: [NULL] Question #8 Assume this declaration: int * arr; Which diagram best describes memory allocation? (CIRCLE ANSWER) a) arr: [int*] b) arr: [int*] --> [NULL] c) arr: [int] --> [NULL] d) arr: [NULL]

10 Question #9 Here is a diagram of memory: Which declaration would generate this? f: [[char*][int]] [[char*][int]] [[char*][int]] // <- assume 3 items contiguous in mem typedef struct char *name; int ssn; Foo; a) Foo f[3]; b) Foo *f[3]; c) Foo **f[3];

11 For the following Questions find the best answer /* QUESTION #1 10 PTS*/ int * getint() int val; printf("enter a number: "); scanf("%d", &val); return( &val ); int * pi; pi = getint(); printf("you entered: %d\n", *pi ); /* QUESTION #3 10 PTS */ #define MAXLEN 5 int i, *curr1, *curr2; int * arr1 = malloc( MAXLEN * sizeof(int) ); int * arr2 = malloc( MAXLEN * sizeof(int) ); arr2[i] = i*2; curr1 = arr1; curr2 = arr2+maxlen-1; while (curr2 >= arr2) *(curr1++) = *(curr2--); printf("%d ", arr1[i] ); printf("\n"); printf("%d ", arr2[i] );

12 free(arr1); free(arr2); /* QUESTION #4 10 PTS */ #define MAXLEN 10 int * arr = malloc( MAXLEN * sizeof(int) ); arr[i] = i*2; printf("%d ", *(arr++) ); free(arr); /* QUESTION #5 10 PTS*/ void Question5(char **wordarray) char **x; wordarray = calloc(10, sizeof(char*)); x=wordarray; for(i=0; i<10; i++) *(x++) = calloc(10, sizeof(char)); strcpy(wordarray[0], "This"); strcpy(wordarray[1], "is"); strcpy(wordarray[2], "a"); strcpy(wordarray[3], "test.");

13 int main( int argc, char *argv[]) char **words; Question5(words); printf("question 10: "); for (i=0; i<10; i++) printf("%s", words[i]); printf("\n"); /* QUESTION #6 10 PTS */ #define MAXLEN 10 int main(int argc, char *argv[] ) int array[ MAXLEN ]; *(array+i) = i; printf( "%d ", *(array+i) ); free (array); /* QUESTION #7 */ #define MAXLEN 10 int main(int argc, char *argv[] ) int *array = malloc( MAXLEN * sizeof(int) );

14 *(array+i) = i; printf( "%d ", *array ); ++array; free (array); /* QUESTION #8 10 PTS*/ int *willy = malloc( 5 * sizeof(int) ); int *willyslast = bar + 4; for (i=0 ; willy<=willyslast; ++willy,++i) *wily = i; /* print willy */ for (i=0 ; i<5 ; ++i) printf("%d ", willy[i] ); free( willy ); /* QUESTION #9 10 PTS*/ How can I declare an array of ints with 5 elements in the array? (circle any/all that apply) a) int arr[5];

15 b) #define MAX 5 int arr[max]; c) int *arr = 1,2,3,4,5 ; d) int *arr = malloc( 5*sizeof(int) ); e) all of the above /* QUESTION #10 10 PTS 2 pts each */ assume: int * x = 1,1,2,4,5; a) What does the expression x+4 produce? b) What does the expression x produce? c) What does the expression &x produce? d) What does the expression *x produce? e) What does the expression *(x+2) produce? Also see other practice test We will discuss some of these problems in class/recitations We can also provide answers later