diff --git a/src/conio/ciolib.h b/src/conio/ciolib.h
index dce561b5ecef4c69bc87bc35f2ef65c6bf794856..c1616cb2cdadc5c962b5bd3a1b231f093b0643d7 100644
--- a/src/conio/ciolib.h
+++ b/src/conio/ciolib.h
@@ -646,7 +646,10 @@ CIOLIBEXPORT int CIOLIBCALL ciomouse_delevent(int event);
 #define CIO_KEY_RIGHT     (0x4d << 8)
 #define CIO_KEY_PPAGE     (0x49 << 8)
 #define CIO_KEY_NPAGE     (0x51 << 8)
+#define CIO_KEY_SHIFT_F(x)((x<11)?((0x53+x) << 8):((0x7c+x) << 8))
+#define CIO_KEY_CTRL_F(x) ((x<11)?((0x67+x) << 8):((0x7e+x) << 8))
 #define CIO_KEY_ALT_F(x)  ((x<11)?((0x67+x) << 8):((0x80+x) << 8))
+#define CIO_KEY_BACKTAB   (0x0f << 8)
 
 #define CIO_KEY_MOUSE     0x7d00	// This is the right mouse on Schneider/Amstrad PC1512 PC keyboards "F-14"
 #define CIO_KEY_QUIT	  0x7e00	// "F-15"
diff --git a/src/conio/cterm.c b/src/conio/cterm.c
index 4a4f9715aa152aec296893c49661769babe80d64..38e96dc63352239ea276546cff69134305534188 100644
--- a/src/conio/cterm.c
+++ b/src/conio/cterm.c
@@ -1405,20 +1405,27 @@ static enum {
 	SEQ_COMPLETE
 } legal_sequence(const char *seq, size_t max_len)
 {
+	size_t intermediate_len;
+
 	if (seq == NULL)
 		return SEQ_BROKEN;
 
 	if (seq[0] == 0)
 		goto incomplete;
 
-	/* Check that it's part of C1 set or part of the Independent control functions */
+	/* Check that it's part of C1 set, part of the Independent control functions, or an nF sequence type (ECMA 35)*/
 	if (seq[0] < 0x40 || seq[0] > 0x7e)
 		return SEQ_BROKEN;
 
+	intermediate_len = strspn(&seq[1+parameter_len], " !\"#$%&'()*+,-./");
+	if (seq[1+intermediate_len] == 0)
+		goto incomplete;
+	if (seq[1+intermediate_len] < 0x30 || seq[1+intermediate_len] > 0x7e)
+		return SEQ_BROKEN;
+
 	/* Check if it's CSI */
 	if (seq[0] == '[') {
 		size_t parameter_len;
-		size_t intermediate_len;
 
 		if (seq[1] >= '<' && seq[1] <= '?')
 			parameter_len = strspn(&seq[1], "0123456789:;<=>?");
@@ -3324,7 +3331,11 @@ static void do_ansi(struct cterminal *cterm, char *retbuf, size_t retsize, int *
 								seq_default(seq, 0, ABS_MINX);
 								seq_default(seq, 1, ABS_MAXX);
 								col = seq->param_int[0];
+								if (col == 0)
+									col = cterm->left_margin;
 								max_col = seq->param_int[1];
+								if (max_col == 0)
+									max_col = cterm->right_margin;
 								if(col >= ABS_MINX && max_col > col && max_col <= ABS_MAXX) {
 									cterm->left_margin = col;
 									cterm->right_margin = max_col;
diff --git a/src/conio/cterm.txt b/src/conio/cterm.txt
index 889b74531b96aae64f7f97efc97839fb87d2c0f8..15246c5ea3cee621f0d593d70dfcf0211ced125b 100644
--- a/src/conio/cterm.txt
+++ b/src/conio/cterm.txt
@@ -1021,6 +1021,7 @@ CSI Pn1 ; Pn2 s
 	Set Left and Right Margins
 	Defaults: Pn1 = 1
 	          Pn2 = last column on screen
+	If either Pn1 or Pn2 is zero, the current setting is retained.
 	Selects left and right margins, defining the scrolling region. Pn1 is
 	the column number of the first column in the scrolling region. Pn2 is
 	the column number of the right column.