ESL supports the ASCII standard 7-bit character set. The ESL character set consists of the following ASCII characters:
| Character | Meaning | Usage | 
| SPACE | Blank | Throughout ESL | 
| A-Z | Uppercase | Throughout ESL | 
| a-z | Lowercase | Throughout ESL | 
| 0-9 | Digits | Throughout ESL | 
| = | Equal sign | Relational operator | 
| != | Not equal sign | Relational operator | 
| + | Plus sign | Arithmetic operator | 
| - | Minus sign | Arithmetic operator | 
| * | Multiplication sign | Arithmetic operator | 
| / | Division sign | Arithmetic operator | 
| \ | Backslash | Escape character | 
| ( | Left parenthesis | Required in expressions | 
| ) | Right parenthesis | Required in expressions | 
| [ | Left bracket | Required in arrays | 
| ] | Right bracket | Required in arrays | 
| # | Number sign | Comment character | 
| , | Comma | Separator in drawing statements | 
| . | Decimal point | Floating point values | 
| < | Less than | Relational operator | 
| <= | Less than or equal to | Relational operator | 
| > | Greater than | Relational operator | 
| >= | Greater than or equal to | Relational operator | 
| “ | Quotation mark | String delimiter | 
| _ | Underscore | Allowed in identifiers | 
| : | Colon | Separator in argument lists and pattern scaling | 
| All characters | 
 | String values |