Abstract: This instantaneous decimal credibility check device enables the operator of a terminal to send out, by means of this terminal, numerical data, the decimal value of which will have been previously checked.It comprises a decimal positioning computer CCD connected to decoders DEC of the program memory M1 and to the keyboard CG for the purpose of receiving information therefrom and driving bistable triggers BS for guiding the keys of the keyboard. The decimal positioning computer is also connected, on the one hand directly to a space codes emitter ECE and decimal point emitter EPtD, and, on the other hand indirectly through certain of the guidance bistable triggers, to the "flag" character emitter ECV. A blind code emitter ECAV is directly connected to a decoder DEC of the instruction character ICAV corresponding to the number "n" of blind codes. A principal memory stores the numerical data, blind codes, space codes and flag characters.