The software of automotive control systems has become increasingly large and complex. High level languages (primarily C) and the compilers become more important to reduce coding time. Most compilers represent real number in the floating-point format specified by IEEE standard 754. Most microprocessors in the automotive industry have no hardware for the operations using the IEEE standard due to the cost limitation, resulting in the slow execution speed and large code size. An alternative format to increase execution speed and reduce code size is proposed. Experimental results for the alternative format show the improvement in execution speed and code size.