C Beginnings

Question 1

How would you get input from the user in C?

Answer 1

scanf(“%d”, &age);

The %d specifies what data type you want
The &age is the location in memory of where you will store your data

Question 2

Issue with scanf()?

Answer 2

It doesn’t get the whole line, you need to use fgets.

Scanf only reads until the first whitespace

Question 3

How to properly use fgets()?

Answer 3

fgets(variable, size of variable, stdin);

Question 4

Issue with fgets()?

Answer 4

It automatically includes a \n

Question 5

How to get rid of the fgets() \n?

Answer 5

import <string.h></string.h>

name[strlen(name)-1] = ‘\0’

Need to
1. import the string
2. make the last digit equal to ‘\0’

Question 6

When would you want to use fgets over scanf?

Answer 6

When you want to accept whitespaces

Question 7

How to get math functions?

Answer 7

include <math.h></math.h>

Question 8

How would you make a switch statement?

Answer 8

switch(grade){
case ‘A’:
printf(“Nice”);
break;
default:
printf(“LOL);
}

Question 9

What do you have to have at the end of every switch case?

Answer 9

A break line.

Question 10

What do you have to add if none of your cases work just in case?

Answer 10

a default: case

Question 11

Show me a ternary operator

Answer 11

(condition) ? value if true : value if false

Question 12

What is a function prototype?

Answer 12

The function’s call method with the required arguments.

• makes sure when a function is called, it has the correct arguments
• C doesn’t check valid arguments were entered so you need these prototypes for it to work

Question 13

strlwr(string)

Answer 13

Converts a string to lowercase

Question 14

strupr(string)

Answer 14

Converst a string to uppercase

Question 15

strcat(String1, String2);

Answer 15

Appends string 2 to string 1

Question 16

strncat(string1, string2, 1);

Answer 16

Appends n characters from string2 to string 1

Question 17

strcpy(string1, string2)

What would strcpy(Nick, Heath) do?

Answer 17

Copy string2 to string1

Make Nick = Heath

Question 18

strncpy(string1, string2, 4);

Answer 18

copy n characters of string2 to string1

Question 19

What is something interesting about these string functions?

Answer 19

They are pointers that change the original variable

Question 20

strset(string1, ‘?’);

Answer 20

sets all characters of a string to a given character

Question 21

strnset(string1, ‘x’, 1);

Answer 21

Sets first n chracters to a string to a given character

Question 22

strrev(string1)

Answer 22

reverses a string

Question 23

strlen(string1);

Answer 23

returns length of string

Question 24

strcmp(string1, string2);

Answer 24

string compare all characters

Return 0 if the same
Return something else if not the same

Question 25

strncmp(string1, string2, 1);

Answer 25

string compare n characters

Question 26

strcmpi(string1, string1);

Answer 26

string compare all (ignore case)

Question 27

strnicmp(string1, string1, 1);

Answer 27

string compare n characters (ignore case)

Question 28

How do we get a array of strings in C?

Answer 28

We need a 2D array

Question 29

char cars[][10] Explain the 10

Answer 29

Each element is 10 chars wide

Question 30

How to iterate a string of arrays?

Answer 30

Use a for loop, for(int i = 0, i < sizeof(cars)/sizeof(cars[0]); i++) printf("%s\n", fruits[i]);

Question 31

How to update a string value in a string array?

Answer 31

Use the strcpy function

Question 32

for(int i = 0, i < sizeof(cars)/sizeof(cars[0]); i++) printf("%s\n", cars[i]); explain this

Answer 32

The sizeof(cars)/sizeof(cars[0]) The first sizeof gets the total bit length of the cars array. For example, if cars[][10] = {4, 3, 2, 1} then each string is 10 bits long and since we have four of them we have 40 bits. The Second sizeof, gets the length of the first one which is 10, which is also true for all of them. Thus when divided we have 4 cars to loop through The printf() then prints out each car since it is a pointer. Note* When it prints out it prints out until it reaches the '\0' which is automatically added at initialization.

Question 33

I have a variable age, how do you declare a pointer to point to age?

Answer 33

int *ptr = &age;

Question 34

I have a ptr to age, how do I print out the age with a ptr?

Answer 34

printf("%d", *ptr);

Question 35

How accept a pointer for a funciton's argument

Answer 35

void accept(int *ptr);

Question 36

If you don't assign a pointer, what is good practice for this?

Answer 36

Assign it to a null

Question 37

How to open a file?

Answer 37

FILE *file = fopen("text", "Mode"):

Question 38

What should you do after done with a file and how to do it?

Answer 38

Close! fclose(fileName);

Question 39

How to print to a file?

Answer 39

fprintf(fileName, "text");

Question 40

How to read from a file?

Answer 40

fgets(whereToReadTo, size, fileName);

Question 41

What is Array Decay?

Answer 41

When we send an array to a function, the array becomes a pointer and could end up messing up whats inside our array since we are changing the values in the array