This note considers codes for computer file transfer protocols when only upper-case ASCII characters are used as control characters. Such a restriction may be necessary to avoid dependence on unique machine features and to promote portability. If ten control functions are needed, a number used in a typical sufficiently rich protocol, we seek a subset of ten upper-case ASCII characters with good distance properties. The control functions form themselves naturally into three groups. Recognizing that only even distances can occur, we wish to make the intragroup minimum distances as large as possible, and the number of control characters having distance 2 as small as possible. We find the optimum solution to the above problem and an assignment that attains the optimum. The codes are essentially unique.