Where is the value of "CblasRowMajor" set and declared in MKL tutorial sample?

In the C version of MKL's tutorial, source file dgemm_example.c, line 71:

    cblas_dgemm(CblasRowMajor, CblasNoTrans, CblasNoTrans, 
                m, n, p, alpha, A, p, B, n, beta, C, n);

Where is the varialble `CblasRowMajor` declared and where is the value of this variable set? I couldn't find any clue about it in the source file. Thank you for your help.