"CompLab" ("Compiler Laboratory") or "ABC" ("Advanced Basic-C") is a double conversion compiler working in two parallel regimes (A and B) one of which is similar to that of MATLAB while the other is a professional compilation routine similar to C and FORTRAN languages. Double-conversion scheme of compilation allows making advantage of both the simplicity of used code (program, commands) and at the same time of the power of C language in speed and in the capacity of CPU memory usage. The "A" regime allows for on-line calculation of multidimensional integrals, eigenvalues of large matrices, roots of nonlinear equations, plotting functions and their derivatives, etc. The "B" regime is an exportable program of conversion from the pseudobasic input code to C-code, compilation and solution. The C-code is fit for usage in any computational platform including Windows, OS/2, Linux and Unix machines.