diff --git a/I1620/i1620_cd.c b/I1620/i1620_cd.c
index 2e6ba2c4..3faa69dc 100644
--- a/I1620/i1620_cd.c
+++ b/I1620/i1620_cd.c
@@ -133,7 +133,7 @@ const char cdr_to_num[128] = {
 
 /* Numeric (flag + digit) to card punch (ASCII) */
 
-const char num_to_cdp[32] = {
+const int8 num_to_cdp[32] = {
  '0', '1', '2', '3', '4', '5', '6', '7',                /* 0 */
  '8', '9', '|', ',', ' ', '"', ' ', '"',
  ']', 'J', 'K', 'L', 'M', 'N', 'O', 'P',                /* F + 0 */
@@ -149,7 +149,7 @@ const char num_to_cdp[32] = {
    12-7-8 (}) reads as 5F
 */
 
-const char cdr_to_alp[128] = {
+const int8 cdr_to_alp[128] = {
  0x00,   -1,   -1,   -1,   -1,   -1,   -1,   -1,        /* 00 */
    -1, 0x00, 0x00,   -1,   -1, 0x00,   -1,   -1,
    -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,        /* 10 */
@@ -186,7 +186,7 @@ const char cdr_to_alp[128] = {
    12-5-8 ([), or 12-6-8 (<)
 */
 
-const char alp_to_cdp[256] = {
+const int8 alp_to_cdp[256] = {
  ' ',  -1, '?', '.', ')',  -1,  -1, '}',                /* 00 */
   -1,  -1, '\'', -1,  -1,  -1,  -1, '"',
  '+',  -1, '!', '$', '*', ']',  -1,  -1,                /* 10 */ 
diff --git a/I1620/i1620_sys.c b/I1620/i1620_sys.c
index 198d29e7..e9c501b0 100644
--- a/I1620/i1620_sys.c
+++ b/I1620/i1620_sys.c
@@ -39,7 +39,7 @@ extern DEVICE dp_dev;
 extern UNIT cpu_unit;
 extern REG cpu_reg[];
 extern uint8 M[MAXMEMSIZE];
-extern char cdr_to_alp[128], alp_to_cdp[256];
+extern int8 cdr_to_alp[128], alp_to_cdp[256];
 
 /* SCP data structures and interface routines
 
@@ -474,7 +474,8 @@ return SCPE_OK;
 t_stat parse_sym (char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw)
 {
 int32 i, qv, opfl, last;
-char t, la, *fptr, gbuf[CBUFSIZE];
+char la, *fptr, gbuf[CBUFSIZE];
+int8 t;
 
 while (isspace (*cptr))                                 /* absorb spaces */
     cptr++;
diff --git a/SDS/sds_stddev.c b/SDS/sds_stddev.c
index 537acca1..b35cbdbf 100644
--- a/SDS/sds_stddev.c
+++ b/SDS/sds_stddev.c
@@ -65,9 +65,9 @@ t_stat tto (uint32 fnc, uint32 inst, uint32 *dat);
 t_stat tto_svc (UNIT *uptr);
 t_stat tto_reset (DEVICE *dptr);
 
-extern const char ascii_to_sds[128];
-extern const char sds_to_ascii[64];
-extern const char odd_par[64];
+extern const int8 ascii_to_sds[128];
+extern const int8 sds_to_ascii[64];
+extern const int8 odd_par[64];
 
 /* PTR data structures
 
diff --git a/SDS/sds_sys.c b/SDS/sds_sys.c
index 1f2a0cef..b446169a 100644
--- a/SDS/sds_sys.c
+++ b/SDS/sds_sys.c
@@ -101,7 +101,7 @@ const char *sim_stop_messages[] = {
 
 /* Character conversion tables */
 
-const char sds_to_ascii[64] = {
+const int8 sds_to_ascii[64] = {
     '0', '1', '2', '3', '4', '5', '6', '7',
     '8', '9', ' ', '=', '\'', ':', '>', '%',            /* 17 = check mark */
     '+', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
@@ -112,7 +112,7 @@ const char sds_to_ascii[64] = {
     'Y', 'Z', '?', ',', '(', '~', '\\', '#'             /* 72 = rec mark */
      };                                                 /* 75 = squiggle, 77 = del */
 
-const char ascii_to_sds[128] = {
+const int8 ascii_to_sds[128] = {
      -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,             /* 0 - 37 */
     032, 072,  -1,  -1,  -1, 052,  -1,  -1,
      -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,
@@ -131,7 +131,7 @@ const char ascii_to_sds[128] = {
     067, 070, 071,  -1,  -1,  -1,  -1,  -1
     };
 
-const char odd_par[64] = {
+const int8 odd_par[64] = {
     0100, 0001, 0002, 0103, 0004, 0105, 0106, 0007,
     0010, 0111, 0112, 0013, 0114, 0015, 0016, 0117,
     0020, 0121, 0122, 0023, 0124, 0025, 0026, 0127,