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Multidimensional arrays

A multidimensional array in C is merely an array whose elements are themselves arrays. The elements of an n-dimensional array are (n-1)-dimensional arrays. For example, each element of a two-dimensional array is a one-dimensional array. The elements of a one-dimensional array, of course, do not have an array type.

A multidimensional array declaration has a pair of brackets for each dimension:

char screen[10][40][80]; // A three-dimensional array.

The array screen consists of the 10 elements screen[0] to screen[9]. Each of these elements is a two-dimensional array, consisting in turn of 40 one-dimensional arrays of 80 characters each. All in all, the array screen contains 32,000 elements with the type char.

Two-dimensional arrays are also called matrices. Because they are so frequently used, they merit a closer look. It is often helpful to think of the elements of a matrix as being arranged in rows and columns. Thus the matrix mat in the following definition has three rows and five columns:

float mat[3][5];

The three elements mat[0], mat[1], and mat[2] are the rows of the matrix mat. Each of these rows is an array of five float elements. Thus the matrix contains a total of 3 x 5 = 15 float elements, as the following diagram illustrates:

0 1 2 3 4
mat[0] 0.0 0.1 0.2 0.3 0.4
mat[1] 1.0 1.1 1.2 1.3 1.4
mat[2] 2.0 2.1 2.2 2.3 2.4

Accessing array elements

The subscript operator [ ] provides an easy way to address the individual elements of an array by index. If myArray is the name of an one dimensional array and i is an integer, then the expression myArray[i]designates the array element with the index i. Array elements are indexed beginning with 0. Thus, if len is the number of elements in an array, the last element of the array has the index len-1.

The following code fragment defines the array myArray and assigns a value to each element.

#define A_SIZE 4 long myarray[A_SIZE]; for (int i = 0; i<A_SIZE; ++i) myarray[i]= 2 * i;

The diagram in [link] illustrates the result of this assignment loop.

Values assigned to elements by index

To access a char element in the three-dimensional array screen, you must specify three indices. For example, the following statement writes the character Z in a char element of the array:

screen[9][39][79] = 'Z';

Initializing arrays

If you do not explicitly initialize an array variable, the usual rules apply: if the array has automatic storage duration, then its elements have undefined values. Otherwise, all elements are initialized by default to the value 0.

  • You cannot include an initialization in the definition of a variable-length array.
  • If the array has static storage duration, then the array initializers must be constant expressions. If the array has automatic storage duration, then you can use variables in its initializers.
  • You may omit the length of the array in its definition if you supply an initialization list. The array's length is then determined by the index of the last array element for which the list contains an initializer. For example, the definition of the array a in the previous example is equivalent to this: int a[ ] = { 1, 2, 4, 8 }; // An array with four elements.
  • If the definition of an array contains both a length specification and an initialization list, then the length is that specified by the expression between the square brackets. Any elements for which there is no initializer in the list are initialized to zero (or NULL, for pointers). If the list contains more initializers than the array has elements, the superfluous initializers are simply ignored.
  • A superfluous comma after the last initializer is also ignored.
  • As a result of these rules, all of the following definitions are equivalent: int a[4] = {1, 2};int a[ ] = {1, 2, 0, 0};int a[ ] = {1, 2, 0, 0, };int a[4] = {1, 2, 0, 0, 5};

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
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John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
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David Reply
what is viscosity?
David
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emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
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Adjanou
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Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
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Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
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Source:  OpenStax, Introduction to computer science. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10776/1.1
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