* ebcd.cpp

const unsigned char os_toascii[256] = {
        0x00, 0x01, 0x02, 0x03, 0x85, 0x09, 0x86, 0x7f, /* 00-0f: */
        0x87, 0x8d, 0x8e, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, /* ................ */
        0x10, 0x11, 0x12, 0x13, 0x8f, 0x0a, 0x08, 0x97, /* 10-1f: */
        0x18, 0x19, 0x9c, 0x9d, 0x1c, 0x1d, 0x1e, 0x1f, /* ................ */
        0x80, 0x81, 0x82, 0x83, 0x84, 0x92, 0x17, 0x1b, /* 20-2f: */
        0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x05, 0x06, 0x07, /* ................ */
        0x90, 0x91, 0x16, 0x93, 0x94, 0x95, 0x96, 0x04, /* 30-3f: */
        0x98, 0x99, 0x9a, 0x9b, 0x14, 0x15, 0x9e, 0x1a, /* ................ */
        0x20, 0xa0, 0xe2, 0xe4, 0xe0, 0xe1, 0xe3, 0xe5, /* 40-4f: */
        0xe7, 0xf1, 0xa2, 0x2e, 0x3c, 0x28, 0x2b, 0x7c, /* ...........<(+| */
        0x26, 0xe9, 0xea, 0xeb, 0xe8, 0xed, 0xee, 0xef, /* 50-5f: */
        0xec, 0xdf, 0x21, 0x24, 0x2a, 0x29, 0x3b, 0x5e, /* &.........!$*);^ */
        0x2d, 0x2f, 0xc2, 0xc4, 0xc0, 0xc1, 0xc3, 0xc5, /* 60-6f: */
        0xc7, 0xd1, 0xa6, 0x2c, 0x25, 0x5f, 0x3e, 0x3f, /* -/.........,%_>? */
        0xf8, 0xc9, 0xca, 0xcb, 0xc8, 0xcd, 0xce, 0xcf, /* 70-7f: */
        0xcc, 0x60, 0x3a, 0x23, 0x40, 0x27, 0x3d, 0x22, /* .........`:#@'=" */
        0xd8, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, /* 80-8f: */
        0x68, 0x69, 0xab, 0xbb, 0xf0, 0xfd, 0xfe, 0xb1, /* .abcdefghi...... */
        0xb0, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 0x70, /* 90-9f: */
        0x71, 0x72, 0xaa, 0xba, 0xe6, 0xb8, 0xc6, 0xa4, /* .jklmnopqr...... */
        0xb5, 0x7e, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, /* a0-af: */
        0x79, 0x7a, 0xa1, 0xbf, 0xd0, 0x5b, 0xde, 0xae, /* .~stuvwxyz...[.. */
        0xac, 0xa3, 0xa5, 0xb7, 0xa9, 0xa7, 0xb6, 0xbc, /* b0-bf: */
        0xbd, 0xbe, 0xdd, 0xa8, 0xaf, 0x5d, 0xb4, 0xd7, /* .............].. */
        0x7b, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, /* c0-cf: */
        0x48, 0x49, 0xad, 0xf4, 0xf6, 0xf2, 0xf3, 0xf5, /* {ABCDEFGHI...... */
        0x7d, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 0x50, /* d0-df: */
        0x51, 0x52, 0xb9, 0xfb, 0xfc, 0xf9, 0xfa, 0xff, /* }JKLMNOPQR...... */
        0x5c, 0xf7, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, /* e0-ef: */
        0x59, 0x5a, 0xb2, 0xd4, 0xd6, 0xd2, 0xd3, 0xd5, /* \.STUVWXYZ...... */
        0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, /* f0-ff: */
        0x38, 0x39, 0xb3, 0xdb, 0xdc, 0xd9, 0xda, 0x9f /* 0123456789...... */
};

const unsigned char os_toebcdic[256] = {
        0x00, 0x01, 0x02, 0x03, 0x37, 0x2d, 0x2e, 0x2f, /* 00-0f: */
        0x16, 0x05, 0x15, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, /* ................ */
        0x10, 0x11, 0x12, 0x13, 0x3c, 0x3d, 0x32, 0x26, /* 10-1f: */
        0x18, 0x19, 0x3f, 0x27, 0x1c, 0x1d, 0x1e, 0x1f, /* ................ */
        0x40, 0x5a, 0x7f, 0x7b, 0x5b, 0x6c, 0x50, 0x7d, /* 20-2f: */
        0x4d, 0x5d, 0x5c, 0x4e, 0x6b, 0x60, 0x4b, 0x61, /* !"#$%&'()*+,-./ */
        0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, /* 30-3f: */
        0xf8, 0xf9, 0x7a, 0x5e, 0x4c, 0x7e, 0x6e, 0x6f, /* 0123456789:;<=>? */
        0x7c, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, /* 40-4f: */
        0xc8, 0xc9, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, /* @ABCDEFGHIJKLMNO */
        0xd7, 0xd8, 0xd9, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, /* 50-5f: */
        0xe7, 0xe8, 0xe9, 0xad, 0xe0, 0xbd, 0x5f, 0x6d, /* PQRSTUVWXYZ[\]^_ */
        0x79, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, /* 60-6f: */
        0x88, 0x89, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, /* `abcdefghijklmno */
        0x97, 0x98, 0x99, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, /* 70-7f: */
        0xa7, 0xa8, 0xa9, 0xc0, 0x4f, 0xd0, 0xa1, 0x07, /* pqrstuvwxyz{|}~. */
        0x20, 0x21, 0x22, 0x23, 0x24, 0x04, 0x06, 0x08, /* 80-8f: */
        0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x09, 0x0a, 0x14, /* ................ */
        0x30, 0x31, 0x25, 0x33, 0x34, 0x35, 0x36, 0x17, /* 90-9f: */
        0x38, 0x39, 0x3a, 0x3b, 0x1a, 0x1b, 0x3e, 0xff, /* ................ */
        0x41, 0xaa, 0x4a, 0xb1, 0x9f, 0xb2, 0x6a, 0xb5, /* a0-af: */
        0xbb, 0xb4, 0x9a, 0x8a, 0xb0, 0xca, 0xaf, 0xbc, /* ................ */
        0x90, 0x8f, 0xea, 0xfa, 0xbe, 0xa0, 0xb6, 0xb3, /* b0-bf: */
        0x9d, 0xda, 0x9b, 0x8b, 0xb7, 0xb8, 0xb9, 0xab, /* ................ */
        0x64, 0x65, 0x62, 0x66, 0x63, 0x67, 0x9e, 0x68, /* c0-cf: */
        0x74, 0x71, 0x72, 0x73, 0x78, 0x75, 0x76, 0x77, /* ................ */
        0xac, 0x69, 0xed, 0xee, 0xeb, 0xef, 0xec, 0xbf, /* d0-df: */
        0x80, 0xfd, 0xfe, 0xfb, 0xfc, 0xba, 0xae, 0x59, /* ................ */
        0x44, 0x45, 0x42, 0x46, 0x43, 0x47, 0x9c, 0x48, /* e0-ef: */
        0x54, 0x51, 0x52, 0x53, 0x58, 0x55, 0x56, 0x57, /* ................ */
        0x8c, 0x49, 0xcd, 0xce, 0xcb, 0xcf, 0xcc, 0xe1, /* f0-ff: */
        0x70, 0xdd, 0xde, 0xdb, 0xdc, 0x8d, 0x8e, 0xdf /* ................ */
};

/* Translate a memory block from EBCDIC (host charset) to ASCII (net charset)
* dest and srce may be identical, or separate memory blocks, but
* should not overlap.
*/
void ebcdic2ascii(void *dest, const void *srce, size_t count)
{
    auto *udest = static_cast<unsigned char *>(dest);
    const auto *usrce = static_cast<const unsigned char *>(srce);
    while (count-- != 0) {
        *udest++ = os_toascii[*usrce++];
    }
}

void ascii2ebcdic(void *dest, const void *srce, size_t count)
{
    auto *udest = static_cast<unsigned char *>(dest);
    const auto *usrce = static_cast<const unsigned char *>(srce);

    while (count-- != 0) {
        *udest++ = os_toebcdic[*usrce++];
    }
}

* hex.cpp

void hex2str(char *out, const char *hex, size_t len) {
    char c;
    int i, j;
    int flag = 0;

#define NEXT_BYTE out[j++]=c; c=0; flag=0
    for (i = 0, j = 0; i <len; i++) {
        if (hex[i] == 0x20 || hex[i] == 0x07 || hex[i] == 0x0a) {
            NEXT_BYTE;
        } else if ('0' <= hex[i] && hex[i] <= '9') {
            c *= 16;
            c += hex[i] - '0';
            flag += 1;
        } else if ('a' <= hex[i] && hex[i] <= 'f') {
            c *= 16;
            c += hex[i] - 'a' + 10;
            flag += 1;
        } else if ('A' <= hex[i] && hex[i] <= 'F') {
            c *= 16;
            c += hex[i] - 'A' + 10;
            flag += 1;
        } else {}
        if (flag > 1) {
            NEXT_BYTE;
        }
    }
    out[j++] = c;
    out[j] = '\0';
}

Usage:

char hex[1024];
    char ebcd[512];
    char ascii[512];

    strcpy(hex,"4040404040f1f8f9c4c2f1f1404040404040404040404040f5f07cd9d7c8c4d94040d9c5d7f0f0f0404040f040404040404040404040404040404040404040404040404040f0404040f1f1f97cd6c4c1e3c14040404040f1f0f5c2c2d6f3f2f4f0f1f2f0f2f3f0f1f1f0f1f0f24040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040404040");
    hex2str(ebcd, hex, strlen(hex));
    // std::cout << ebcd << "\n";
    ebcdic2ascii(ascii, ebcd, strlen(ebcd));
    std::cout << "[" << ascii << "]\n";