C Programming Module 7: Arrays

Module 7: Arrays

• Arrays are used to store multiple values of the same data type.
• Unlike scalar variables, which hold a single value, arrays hold a collection of related values.
• A single-dimensional array is a list of individual items of the same scalar data type.
• Arrays are stored in contiguous memory locations
• Elements in an array are accessed by their position (index)
• The index starts at 0.
• Arrays can be initialized during declaration.
• Initializing is done by listing values within braces, separated by commas

Learning Objectives

• Understand and manipulate arrays in C.

Outline

• Lesson 7.1: One-Dimensional Arrays
  • Input and Output of Array Values
• Lesson 7.2: Array Initialization
• Lesson 7.3: Arrays as Function Arguments
• Lesson 7.4: Two-Dimensional Arrays

Overview

• Scalar variables store a single value at a time. A scalar is an atomic type, which can't be subdivided. A set of values of the same data type can be logically grouped
• Arrays are a collection of values of the same data type
• Single-dimensional arrays organize and store data.
• Multi-dimensional arrays are also studied and how to declare and use such arrays.

Summary: Single-Dimensional Array

• Data structure to store a list of values of the same data type
• Declared by specifying the data type and the size.
• Example: int num [100]. This creates an integer array of size 100.
• Use constants for array size to avoid retyping.
  • Example: #define MAXSIZE 100, then int num [MAXSIZE].

Summary: Single-Dimensional Array (Continued)

• Array elements are stored in consecutive memory locations
• Elements are accessed through their index.
• Example: num[22].
• Subscripts start at 0 (the first element), following sequentially upwards.
• Arrays can be initialized during declaration:
• Example: int nums[] = {3, 7, 8, 15};

Summary: Single-Dimensional Array (Continued)

• Arrays are passed to functions by passing their name as an argument.
• The function receives the address of the first array element(not a copy), ensuring modifications made to array elements affect original
• Size of the array can be omitted in function parameters.

Summary: Two-Dimensional Arrays

• Declared by specifying both row and column sizes
• Example: int mat [ROWS][COLS] ,where ROWS is the number of rows and COLS the number of columns.
• Can be initialized during declaration, with values listed row by row within braces, separated by commas;
• Example: int vals[ROWS][COLS] = { {1, 2}, {3,4}, {5, 6} };.

Summary: Two-Dimensional Arrays (Continued)

• Arrays are passed to functions by passing the array name as an argument.
• The row size can sometimes be omitted from the parameter declaration but, the column size must still be specified.
• Arrays are stored in row-wise order in memory

Lesson 7.1: One-Dimensional Arrays

• Arrays, in C, are collections of values of the same data type.
• Each array element is stored in contiguous memory locations
• Elements can be accessed based on their index.
• In C, elements are accessed using their position/index, using brackets.

Input and Output of Array Values

• Array elements can be assigned values using individual assignment statements, or through scanf() function.
  • Example: price [5] = 10.69 ;
  • Example: scanf (“%d %lf”, &grades[0], &price[2] )
• For input, use for statements to loop through the array for interactive entry of values.

Input and Output of Array Values (Continued)

• for statement used for accessing and displaying array elements and performing operations such as adding up elements.
• In C, array indices can't be checked by the compiler.
• You need to be careful with the bounds of an array to avoid errors.

Lesson 7.2: Array Initialization

• Arrays, like scalar variables, can be declared inside or outside a function.
• Local arrays - within functions
• Global Arrays - declared outside functions
• Static arrays-declared as static. Static arrays retain their values until the program ends.

Lesson 7.2: Array Initialization (Continued)

• Initializers - values assigned in declarations. They are listed in the order they appear in the array, for example when declaring int grades [5] = {98, 87, 92, 79, 85} ;
• Whitespace, such as tabs (\t), newlines, (\n), and spaces are ignored by C in initialization.
• When there are fewer initializers than array elements in declaration, remaining elements are set to 0.
• Arrays can have their sizes omitted when initialized. The compiler automatically detects the size from the declaration's initializers values.

Lesson 7.2: Array Initialization (Continued)

• Character arrays - can be initialized with strings omitting the brackets and commas.
• A \0 is automatically appended to the end of the initializer to mark the end of the string.

Lesson 7.3: Arrays as Function Arguments

• Passing Individual Array Elements - passing values to functions. Any changes within the function do not affect the original array.
• Passing the Entire Array - the function receives the original data. Changes inside the function directly affect the original array.

Lesson 7.4: Two-Dimensional Arrays

• Arrays are tables with rows and columns.
• Initializations are row-by-row, similar to one-dimensional arrays. The inner braces can be omitted for simplicity.

Lesson 7.4: Two-Dimensional Arrays (Continued)

• Passing 2D arrays to functions works similarly to 1D arrays; passing a reference (not a copy) to the whole array allows direct modifications to the original array in the function.

Assignment 4

• Practical uses of 1D arrays: storing lists of grades, prices of items, etc.
• Explain reasoning.
• Practical uses of 2D arrays: storing game boards, spreadsheet data, etc.
• Explain reasoning.
• Important considerations regarding plagiarism.