Two-dimensional Arrays
Suppose you need to write a program that stores the student ID
numbers of 20 students and then the grades for each of them on
three different tests. You could create 4 parallel arrays to hold
this data; but, it would be nice to put the test grades all into one
storage structure. Something like the table below:
ids[20]
test_grades[20][3]
12345
89
90
92
23456
78
85
73
34567
100
98
91
‘’
45678
…
…
65
71
…
…
50
test_grades has two indexes: leftmost (20) = row index/size
rightmost (3) = column index/size
C - Strings
The ‘string’ type we have been using is really
something called a class. We have used them
without really knowing what they are. You will get to
classes in the next course.
The ‘string’ C++ class was not always a part of the C++
language. Before that strings were always
implemented as an array of char. Literals (as we have
previously discussed) are stored this way.
So – for now to have an array of strings, we will
implement them as two-dimensional arrays of char.
String: An array of char (C-Strings)
C-Strings are actually single dimensional arrays of char
char name[6] = “Trish”;
Name is stored as an array of char with size 6
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So, an array of c-strings is really a two-dimensional array
of char names[3][10];
could store 3 names with a maximum length of 9
characters
Each string in the array can be referenced by referring
to its row number.
Visual Look at names[5][11]
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names[0] == “Espresso”
names[1] == “Mocha Java”
names[2] == “Columbian”
names[3] == “Decaf”
names[4] == “House”
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