How does Lcdstring get the acsii character from the look-up table?

Projects Programming
1

I'm playing around with a Nokia 3310 LCD, trying to figure out how to create bigger fonts.

Could someone explain how Lcdstring ("abcd"); knows how to get the correct ascii letter from the look-up table?

Here is a bit of the look-up table. How does the code know that the letter a is 0x20, 0x54, 0x54, 0x54, 0x78, b is 0x7f, 0x48, 0x44, 0x44, 0x38, and so on?

static const byte ASCII[][5] =
{
{0x20, 0x54, 0x54, 0x54, 0x78} // 61 a
,{0x7f, 0x48, 0x44, 0x44, 0x38} // 62 b
,{0x38, 0x44, 0x44, 0x44, 0x20} // 63 c
,{0x38, 0x44, 0x44, 0x48, 0x7f} // 64 d

Or does // mean something else in this case?

2

The clue is in the "61" (which is just a comment), it probably subtracts. Maybe something as simple as

int index_into_lookup = input_string[char_I_Want] - 'a';