There was a left over.

programs/abs-floating/info.json

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+{
+  "language": "C",
+  "name": "演習課題2 浮動小数点数版",
+  "description": "倍精度浮動小数点数を読み込み、その絶対値を出力するプログラム。",
+  "output": {
+    "type": "screenshot",
+    "content": "./assets/abs-floating.png"
+  },
+  "note": ""
+}

programs/abs-floating/main.c

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+#include <stdio.h>
+
+int main(void) {
+    double x, y;
+
+    printf("Input floating point: ");
+    scanf("%lf", &x);
+
+    y = x;
+
+    if (y < 0.0)
+        y = -y;
+
+    printf("Absolute value of %lf is %lf.\n", x, y);
+
+    return 0;
+}