C Arrays
Array is a kind of data structure that can store a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.
Instead of declaring individual variables, such as number0, number1 and number99, you declare one array variable such as numbers and use numbers[0], numbers[1], , numbers[99] to represent individual variables. A specific element in an array is accessed by an index which starts from 0.
All arrays consist of contiguous memory locations. The lowest address corresponds to the first element and the highest address to the last element.
C Functions and Arrays
In C programming, a single array element or an entire array can be passed to a function. A single value will be passed by value, whereas when passing the whole array, it is always passed as a reference to the first element of the array.
Objective:
You will learn how to use arrays and functions in C.
Preparation (before the lab): Please refer to lab#1.
Procedure:
- Locate the c and lab2b.c files in the zip file that this lab document came in.
- Compile c with gcc using the following command: gcc o lab2a lab2a.c
- What is the output of the program? Can you change it to 2?
Note: The output should be related to the ageArray such as an element in ageArray.
- What is the purpose of the operator sizeof? What datatype will sizeof give 1 value for on all architectures?
- Can you get the number of elements in ageArray? To produce the following output:
2
Size of the array is 4
Modify the main function, write it below and show your labTA the output.
Note: The output 2 and size of array (i.e., 4 (four)) should be related to ageArray such as an element in ageArray and the number of elements in ageArray.
- Compile c with gcc using the following command: gcc o lab2b lab2b.c
- Can you give 2 ways of displaying the stored value and address value of the first element of an array?
- Can you define the function hexToDecimal(char hex[], size_t size) in the lab2b.c using pointers to traverse the array? Write your function below and show your labTA the output.
Note: You are not allowed to use strtoul, strtol, or other functions from stdlib.h.
Hint: Reading from the back of array is easier. Furthermore, you are already given the function hexVal(char hex) to simplify your work.
- Why do we pass the size of the array to the hexToDecimal function in lab2b.c? Can we calculate the size of the array inside the function?
- What is the format specifier to print a variable of datatype size_t?
Marking Scheme: Report 5 marks; correct output 5 marks; Total: 10 marks.
Program lab2a.c
| #include <stdio.h> void display(int); int main() {int ageArray[] = { 2, 15, 4 }; display(ageArray[2]); return 0;}void display(int age) { printf(%d , age);} |
Program lab2b.c
| #include <stdio.h>#include <string.h>#include <ctype.h> int hexToDecimal(char[], size_t); int hexVal(char); int main(void) {char hex[8];size_t len; printf(Enter up to 7 hexadecimal characters: );fgets(hex, 8, stdin);len = strlen(hex); /* End-of-Line Check */ if(hex[len-1] == ) { len = len 1;hex[len] = ;} printf(You entered: %s , hex);printf(The value in decimal is: %d , hexToDecimal(hex, len)); return 0;} |
| int hexVal(char hex) { switch(toupper(hex)) { case 0: return 0; case 1: return 1; case 2: return 2; case 3: return 3; case 4: return 4; case 5: return 5; case 6: return 6; case 7: return 7; case 8: return 8; case 9: return 9; case A: return 10; case B: return 11; case C: return 12; case D: return 13; case E: return 14; case F: return 15;}return 0;}int hexToDecimal(char hex[], size_t size) {// complete the function body return 0;} |
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