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>> SPEAKER: Recall that everything
underneath the hood of a computer is

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stored using bits.

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And bits, in turn, can be used
to represent numbers.

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And numbers, in turn, can be used
to represent characters.

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In fact, there exists a conventional
mapping between those numbers and

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letters, called ASCII--

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American Standard Code for
Information Interchange.

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>> Now with C, it turns out that we can see
this equivalence, because we not

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only have ints, we also have chars, both
of which at the end of the day

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are represented as numbers
and, in turn, bits.

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So let's write a simple program that
simply tells me what the mapping is

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between numbers and letters, keeping in
mind that 65 is a capital A and 97

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is a lower case a.

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Let's begin.

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>> "include standard I/O dot h." "int
main void." And now I'd like to

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iterate over all of the capital letters
printing out their numeric and

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character equivalents.

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So for this, I'll use a "for" loop.

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"for int i gets--

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and now, rather than start at the usual
0, why don't I start at a value

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I know to be significant,
like 65 for capital A?

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Let's do this, so long
is i is less than--

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um--

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65 plus 26, because I know there
are 26 letters in the alphabet.

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And then on each iteration of this
loop, let me increment i by 1.

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>> Now, on each iteration of this
loop, what do I want to do?

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I'd like to print out what the current
number is i and what the

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corresponding char is.

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Now, to achieve that, I can cast, so
to speak, the int to a char in the

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following way.

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"print f %i is %c backslash n" In
other words, I want to say, this

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number is this character.

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So I need to plug in two values to this
place holders for print f, so

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I'll do comma i, comma--

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>> Now, I don't have a variable c or
a char, but I do have a number.

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And I know that numbers can be mapped to
letters, I simply need to tell the

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computer to do that.

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And so I can cast i from an int to
a char, simply by specifying in

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parentheses that I'd indeed like
to convert it to a char.

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>> Let's close now this statement, save
the file, and compile this program.

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"make ascii 0 dot slash ascii 0." And
very quickly print it to the screen as

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this mapping between numbers and
their character equivalents.

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In fact, if I scroll back up, I first
see that 65 is A, 66 is B, and if I

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scroll back down, 90 is Z.

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