This structure is used to have a piece of code execute a
preknown number of times to be executed.
Common form:
for([create counter variable]; [repeat condition]; [modify counter variable])
{
[code to be executed repeatedly]]
}
where [create counter variable] a variable with
variable name of your choice is created and given a value.
Commonly used variable names for a for statement are "i", "j", "k"
because these have very short names, which in many cases read comfortably.
Also "index", "count" or "counter" are often used.
The variable type is usually int.
The value with which the counter is filled depends on what you
are programming. In many cases it has the value 0.
Examples:
int i = 0
int j = 100
Then [repeat condition]: this code to be executed is repeated
repeated for as long as the value true comes out of the condition.
In this, you refer to the counter variable.
Examples:
i < 10
j > 0
[adjust counter variable]
Increasing or decreasing the counter. It is often increased or decreased by 1, sometimes in larger increments (e.g., 10`).
Examples:
i = i + 1
j = j - 10
[code to be executed repeatedly]
The piece of code (this can be several lines of code) to be executed as long as the repeat condition is "true" (true).
Every for statement can be converted to a while statement
that does the same thing, and vice versa.
for(int i =0 ; i < 10 ; i = i + 1)
{
MessageBox.Show(“Test”);
}
Variable i is initially assigned the value 0 and it is immediately stopped when i is assigned the value 10. The code is thus passed with the values 0,1,2,3,4,5,6,7,8 and 9. Therefore, 10 message boxes are displayed with the text "Test".
for(int i =5;i > 0; i = i - 1)
{
MessageBox.Show(“Test”);
}
Variable i is initially assigned the value 5 and it is immediately stopped when i is assigned the value 0. The code is thus passed with the values 5,4,3,2,1. Therefore, 5 message boxes are displayed with the text "Test".
for(int i =0;i < 10;++i)
{
MessageBox.Show(“Test”);
}
The same result as the first example,
but in a shortened notation:
i = i + 1;
is traditionally also written as
i++;
or
++i;
The same result as the second example,
but in an abbreviated writing mode:
for(int i =5;i > 0; --i)
{
MessageBox.Show(“Test”);
}
i=i-1;
is traditionally also written as
i--;
or
--i;
The code
for(int i =0;i < 10; ++i)
{
MessageBox.Show("Test ”+i);
}
results in MessageBoxes
appear with successively:
“Test 0”
“Test 1”
“Test 2”
“Test 3”
“Test 4”
“Test 5”
“Test 6”
“Test 7”
“Test 8”
“Test 9”
The code
for(int i =5;i > 0; i = i - 2)
{
MessageBox.Show("Test ”+i);
}
make messageboxes appear with sequentially:
“Test 5”
“Test 3”
“Test 1”
and finally gives
for(int y =0;y < 2; ++y)
{
for(int x =0;x < 3; ++x)
{
MessageBox.Show(“(”+x+“,”+y+“)”);
}
}
as a result MessageBoxes appear with:
“(0,0)”
“(1,0)”
“(2,0)”
“(0,1)”
“(1,1)”
“(2,1)”