fundamentals of programming€¦ · fundamentals of programming session 17 c arrays. remember:...
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Fundamentals of Programmingsession 17
C Arrays
Remember: count the ratings
1: Bad
2: Average
3: Good
4: Excellent
What if there are 20 numbers?
1:
2:
3:
:
20:
What if there are 100 numbers?
1:
2:
3:
:
100:
What if there are a million numbers?
1:
2:
3:
:
1000000:
C Arrays
2100
2096
2092
2088
int a[7];
Memory
C Arrays
2100
2096
2092
2088
int a[7];
a[1] = 123;
Memory
C Arrays123
2100
2096
2092
2088
int a[7];
a[1] = 123;
Memory
C Arrays
a[3]
a[2]
a[1]
a[0]
2100
2096
2092
2088
int a[7];
a[1] = 123;
a[6]
a[5]
a[4]
Memory
index, subscript
C Arrays
100
?
?
-1
2100
2096
2092
2088
int a[7];
a[0] = -1; a[3] = 100;a[6] = 200;
200
?
?
Memory
C Arrays
100
?
?
-1
2100
2096
2092
2088
int a[7];
a[0] = -1; a[3] = 100;a[6] = 200;
a[7] = 700;
200
?
?
Memory
Initialize Arrays
40
30
20
10
2100
2096
2092
2088
int a[7] = {10,20,30,40,50,60,70};
70
60
50
Memory
Initialize Arrays
0
30
20
10
2100
2096
2092
2088
int a[7] = {10,20,30};
0
0
0
Memory
Initialize Arrays
0
0
0
0
2100
2096
2092
2088
int a[7] = {0};
0
0
0
Memory
So what?
100
?
?
-1
2100
2096
2092
2088
int a[7];
a[0] = -1; a[3] = 100;a[6] = 200;
200
?
?
Memory
difference with ordinary variables
200
?
?
-1
2100
2096
2092
2088
int a[7];
a[0] = -1; a[3] = 100;a[6] = 200;
int i = 3;a[i] = 200;
i += 2;a[i] = i*i*i;
a[i+1] = 300;
300
125
?
Memory
difference with ordinary variables
200
?
?
-1
2100
2096
2092
2088
int a[7];
a[0] = -1; a[3] = 100;a[6] = 200;
int i = 3;a[i] = 200;
i += 2;a[i] = i*i*i; 200
125
?
Memory
difference with ordinary variables
?
?
?
?
2100
2096
2092
2088
int a[7];
for (int i = 0; i < 7; i++) { a[i] = i*i;}
?
?
?
Memory
difference with ordinary variables
9
4
1
0
2100
2096
2092
2088
int a[7];
for (int i = 0; i < 7; i++) { a[i] = i*i;}
for (int i = 0; i < 7; i++) { printf("%d\n", a[i]);}
36
25
16
Memory
array1.c
Back to our problemget students scores (all integers {0,1,2,...,19,20}, no fractions). For each number 0,1,2,....,20 print the number of students with this score.
Back to our problemget students scores (all integers {0,1,2,...,19,20}, no fractions). For each number 0,1,2,....,20 print the number of students with this score.
Back to our problemget students scores (all integers {0,1,2,...,19,20}, no fractions). For each number 0,1,2,....,20 print the number of students with this score.
Back to our problemget students scores (all integers {0,1,2,...,19,20}, no fractions). For each number 0,1,2,....,20 print the number of students with this score.
Back to our problemget students scores (all integers {0,1,2,...,19,20}, no fractions). For each number 0,1,2,....,20 print the number of students with this score.
Back to our problemget students scores (all integers {0,1,2,...,19,20}, no fractions). For each number 0,1,2,....,20 print the number of students with this score.
countarray3.c
Change the code so that grades are between 0 and 100.
Change the code so that grades are between 0 and 100.
countarray4.c
Is N a variable?
countarray4.c
Is N a variable?
Let's look at the preprocessor output:
$ gcc -E countarray4.c
countarray4.c
Only works for initializing to zero!
Draw a Histogram instead.
countarray4.c
countarray4.c countarrayhist.c
countarrayhist.c countarrayhist2.c
Roll a dice N times!