A TTable sets up each step of the evaluation of an expression. The lefthandside column holds the current version of the expression according to its current evaluation progress. The righthandside holds the operation and assignment of the current step.
The table is called a TTable because each step assigns a variable starting with a t, short for temporary.
The list in operation column is called the TForm of the expression.
Example
The following is the TTable for the arithmetic expression x^2 + 5*x
.
Expression  Operation 

x^2 + 5*x 

t1 + 5*x 
t1 = x ^ 2 
t1 + t2 
t2 = 5 * x 
t3 
t3 = t1 + t2 
Thus, the TForm of x^2 + 5*x
is
t1 = x ^ 2
t2 = 5 * x
t3 = t1 + t2
Algorithm
The algorithm for creating a TForm from an expression is the automatic programming algorithm.
1to1 mapping
It is possible to convert back and forth between an expression and its TForm. This can be set up in a reverse TTable.
Example
The reverse TTable of
t1 = x ^ 2
t2 = 5 * x
t3 = t1 + t2
is
Expression  Operation 

t3 
t3 = t1 + t2 
t1 + t2 
t2 = 5 * x 
t1 + 5*x 
t1 = x ^ 2 
x^2 + 5*x 
The expression is
x^2 + 5*x
Readability Parenthesis
If an expression constains a parenthesis that is added for readability, the paranthesis can be preserved using an assignment without an operator.
Example
a + (b*c)
:
Expression  Operation 

a + (b*c) 

a + (t1) 
t1 = b*c 
a + t2 
t2 = t1 
t3 
t3 = a + t2 
The assignment to t2 is interpreted as a parenthesis.