Problem:
Listed in Range A11:B13 are characters and their corresponding codes.
Upper case and lower case forms of the same letter are assigned two different codes.
How could we find the exact code in Range A2:B7 matching each character in Range A11:B13?

Solution:
Use the EXACT function to determine whether one of the characters in Range A2:B7 matches exactly (case sensitive) to the lookup character in Range A11:B13.
Then, providing an identical chahrcter was found in Range A2:B7, use the INDEX and MATCH functions to retrieve the code corresponding to that character.
Following is the combined Array Formula:
{=INDEX($B$2:$B$7,MATCH(TRUE,EXACT(A11,$A$2:$A$7),0))}

(To create Array formula: select the cell after typing the formula,press F2 and then press Ctrl+Shift+Enter)

Example:
Range1

Character_________Code
A_________________65
a_________________97
B_________________66
b_________________98
C_________________67
c_________________99

Range2

Character______Code
A______________65
b______________98
C______________67