help - how can i use condition ?

Hello everyone;

I would like to create a column1 in a table from another column0;
Column1 must contain letters as follows:
If a text field in column 0 starts with the letter A write A in column 1 if this field begins with the letter b write b otherwise write c.
I try the IF function but it accepts only one condition;
I also used the SWITCH function but it does not support the character strings;
Your suggestions?